suricata: Change midstream policy to "pass-flow"

[ipfire-2.x.git] / config / cfgroot / ids-functions.pl

#!/usr/bin/perl -w
############################################################################
#                                                                          #
# This file is part of the IPFire Firewall.                                #
#                                                                          #
# IPFire is free software; you can redistribute it and/or modify           #
# it under the terms of the GNU General Public License as published by     #
# the Free Software Foundation; either version 2 of the License, or        #
# (at your option) any later version.                                      #
#                                                                          #
# IPFire is distributed in the hope that it will be useful,                #
# but WITHOUT ANY WARRANTY; without even the implied warranty of           #
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            #
# GNU General Public License for more details.                             #
#                                                                          #
# You should have received a copy of the GNU General Public License        #
# along with IPFire; if not, write to the Free Software                    #
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA #
#                                                                          #
# Copyright (C) 2018-2019 IPFire Team <info@ipfire.org>                    #
#                                                                          #
############################################################################

use strict;

package IDS;

require '/var/ipfire/general-functions.pl';
require "${General::swroot}/network-functions.pl";
require "${General::swroot}/suricata/ruleset-sources";

# Load perl module to deal with Archives.
use Archive::Peek::Libarchive;

# Load perl module to deal with files and path.
use File::Basename;

# Load module to move files.
use File::Copy;

# Load module to recursely remove files and a folder.
use File::Path qw(rmtree);

# Load module to get file stats.
use File::stat;

# Load module to deal with temporary files.
use File::Temp;

# Load module to deal with the date formats used by the HTTP protocol.
use HTTP::Date;

# Load the libwwwperl User Agent module.
use LWP::UserAgent;

# Load function from posix module to format time strings.
use POSIX qw (strftime);

# Load module to talk to the kernel log daemon.
use Sys::Syslog qw(:DEFAULT setlogsock);

# Location where all config and settings files are stored.
our $settingsdir = "${General::swroot}/suricata";

# File where the main file for providers ruleset inclusion exists.
our $suricata_used_rulesfiles_file = "$settingsdir/suricata-used-rulesfiles.yaml";

# File where the addresses of the homenet are stored.
our $homenet_file = "$settingsdir/suricata-homenet.yaml";

# File where the addresses of the used DNS servers are stored.
our $dns_servers_file = "$settingsdir/suricata-dns-servers.yaml";

# File where the HTTP ports definition is stored.
our $http_ports_file = "$settingsdir/suricata-http-ports.yaml";

# File which stores the configured IPS settings.
our $ids_settings_file = "$settingsdir/settings";

# File which stores the used and configured ruleset providers.
our $providers_settings_file = "$settingsdir/providers-settings";

# File which stores the configured settings for whitelisted addresses.
our $ignored_file = "$settingsdir/ignored";

# File which stores HTTP Etags for providers which supports them
# for cache management.
our $etags_file = "$settingsdir/etags";

# Location where the downloaded rulesets are stored.
our $dl_rules_path = "/var/cache/suricata";

# File to store any errors, which also will be read and displayed by the wui.
our $storederrorfile = "/tmp/ids_storederror";

# File to lock the WUI, while the autoupdate script runs.
our $ids_page_lock_file = "/tmp/ids_page_locked";

# Location where the rulefiles are stored.
our $rulespath = "/var/lib/suricata";

# Location where the default rulefils are stored.
our $default_rulespath = "/usr/share/suricata/rules";

# Location where the addition config files are stored.
our $configspath = "/usr/share/suricata";

# Location of the classification file.
our $classification_file = "$configspath/classification.config";

# Location of the sid to msg mappings file.
our $sid_msg_file = "$rulespath/sid-msg.map";

# Location to store local rules. This file will not be touched.
our $local_rules_file = "$rulespath/local.rules";

# File which contains the rules to whitelist addresses on suricata.
our $whitelist_file = "$rulespath/whitelist.rules";

# File which contains a list of all supported ruleset sources.
# (Sourcefire, Emergingthreads, etc..)
our $rulesetsourcesfile = "$settingsdir/ruleset-sources";

# The pidfile of the IDS.
our $idspidfile = "/var/run/suricata.pid";

# Location of suricatactrl.
my $suricatactrl = "/usr/local/bin/suricatactrl";

# Prefix for each downloaded ruleset.
my $dl_rulesfile_prefix = "idsrules";

# Temporary directory to download the rules files.
my $tmp_dl_directory = "/var/tmp";

# Temporary directory where the rulesets will be extracted.
my $tmp_directory = "/tmp/ids_tmp";

# Temporary directory where the extracted rules files will be stored.
my $tmp_rules_directory = "$tmp_directory/rules";

# Temporary directory where the extracted additional config files will be stored.
my $tmp_conf_directory = "$tmp_directory/conf";

# Array with allowed commands of suricatactrl.
my @suricatactrl_cmds = ( 'start', 'stop', 'restart', 'reload', 'fix-rules-dir' );

# Array which contains the HTTP ports, which statically will be declared as HTTP_PORTS in the
# http_ports_file.
my @http_ports = ('80', '81');

# Array which contains a list of rulefiles which always will be included if they exist.
my @static_included_rulefiles = ('local.rules', 'whitelist.rules');

# Array which contains a list of allways enabled application layer protocols.
my @static_enabled_app_layer_protos = ('app-layer', 'decoder', 'files', 'stream');

# Hash which allows to convert the download type (dl_type) to a file suffix.
my %dl_type_to_suffix = (
        "archive" => ".tar.gz",
        "plain" => ".rules",
);

# Hash to translate an application layer protocol to the application name.
my %tr_app_layer_proto = (
        "ikev2" => "ipsec",
        "krb5" => "kerberos",
);

#
## Function to check and create all IDS related files, if the does not exist.
#
sub check_and_create_filelayout() {
        # Check if the files exist and if not, create them.
        unless (-f "$suricata_used_rulesfiles_file") { &create_empty_file($suricata_used_rulesfiles_file); }
        unless (-f "$ids_settings_file") { &create_empty_file($ids_settings_file); }
        unless (-f "$providers_settings_file") { &create_empty_file($providers_settings_file); }
        unless (-f "$whitelist_file" ) { &create_empty_file($whitelist_file); }
}

#
## Function to get a list of all available ruleset providers.
##
## They will be returned as a sorted array.
#
sub get_ruleset_providers() {
        my @providers;

        # Loop through the hash of providers.
        foreach my $provider ( keys %IDS::Ruleset::Providers ) {
                # Add the provider to the array.
                push(@providers, $provider);
        }

        # Sort and return the array.
        return sort(@providers);
}

#
## Function to get a list of all enabled ruleset providers.
##
## They will be returned as an array.
#
sub get_enabled_providers () {
        my %used_providers = ();

        # Array to store the enabled providers.
        my @enabled_providers = ();

        # Read-in the providers config file.
        &General::readhasharray("$providers_settings_file", \%used_providers);

        # Loop through the hash of used_providers.
        foreach my $id (keys %used_providers) {
                # Skip disabled providers.
                next unless ($used_providers{$id}[3] eq "enabled");

                # Grab the provider handle.
                my $provider = "$used_providers{$id}[0]";

                # Add the provider to the array of enabled providers.
                push(@enabled_providers, $provider);
        }

        # Return the array.
        return @enabled_providers;
}

#
## Function to get a hash of provider handles and their configured modes (IDS/IPS).
#
sub get_providers_mode () {
        my %used_providers = ();

        # Hash to store the providers and their configured modes.
        my %providers_mode = ();

        # Read-in the providers config file.
        &General::readhasharray("$providers_settings_file", \%used_providers);

        # Loop through the hash of used_providers.
        foreach my $id (keys %used_providers) {
                # Skip disabled providers.
                next unless ($used_providers{$id}[3] eq "enabled");

                # Grab the provider handle.
                my $provider = "$used_providers{$id}[0]";

                # Grab the provider mode.
                my $mode = "$used_providers{$id}[4]";

                # Fall back to IDS if no mode could be obtained.
                unless($mode) {
                        $mode = "IDS";
                }

                # Add details to provider_modes hash.
                $providers_mode{$provider} = $mode;
        }

        # Return the hash.
        return %providers_mode;
}

#
## Function for checking if at least 300MB of free disk space are available
## on the "/var" partition.
#
sub checkdiskspace () {
        # Call diskfree to gather the free disk space of /var.
        my @df = &General::system_output("/bin/df", "-B", "M", "/var");

        # Loop through the output.
        foreach my $line (@df) {
                # Ignore header line.
                next if $line =~ m/^Filesystem/;

                # Search for a line with the device information.
                if ($line =~ m/dev/ ) {
                        # Split the line into single pieces.
                        my @values = split(' ', $line);
                        my ($filesystem, $blocks, $used, $available, $used_perenctage, $mounted_on) = @values;

                        # Check if the available disk space is more than 300MB.
                        if ($available < 300) {
                                # Exit function and return the available disk space.
                                return $available;
                        }
                }
        }

        # Everything okay, return nothing.
        return;
}

#
## This function is responsible for downloading the ruleset for a given provider.
##
## * At first it initialize the downloader and sets an upstream proxy if configured.
## * The next step will be to generate the final download url, by obtaining the URL for the desired
##   ruleset and add the settings for the upstream proxy.
## * Finally the function will grab the rule file or tarball from the server.
##   It tries to reduce the amount of download by using the "If-Modified-Since" HTTP header.
#
## Return codes:
##
## * "no url" - If no download URL could be gathered for the provider.
## * "not modified" - In case the already stored rules file is up to date.
## * "incomplete download" - When the remote file size differs from the downloaded file size.
## * "$error" - The error message generated from the LWP::User Agent module.
#
sub downloadruleset ($) {
        my ($provider) = @_;

        # The amount of download attempts before giving up and
        # logging an error.
        my $max_dl_attempts = 3;

        # Read proxysettings.
        my %proxysettings=();
        &General::readhash("${General::swroot}/proxy/settings", \%proxysettings);

        # Init the download module.
        #
        # Request SSL hostname verification and specify path
        # to the CA file.
        my $downloader = LWP::UserAgent->new(
                ssl_opts => {
                        SSL_ca_file     => '/etc/ssl/cert.pem',
                        verify_hostname => 1,
                }
        );

        # Set timeout to 10 seconds.
        $downloader->timeout(10);

        # Check if an upstream proxy is configured.
        if ($proxysettings{'UPSTREAM_PROXY'}) {
                my $proxy_url;

                $proxy_url = "http://";

                # Check if the proxy requires authentication.
                if (($proxysettings{'UPSTREAM_USER'}) && ($proxysettings{'UPSTREAM_PASSWORD'})) {
                        $proxy_url .= "$proxysettings{'UPSTREAM_USER'}\:$proxysettings{'UPSTREAM_PASSWORD'}\@";
                }

                # Add proxy server address and port.
                $proxy_url .= $proxysettings{'UPSTREAM_PROXY'};

                # Setup proxy settings.
                $downloader->proxy(['http', 'https'], $proxy_url);
        }

        # Grab the download url for the provider.
        my $url = $IDS::Ruleset::Providers{$provider}{'dl_url'};

        # Check if the provider requires a subscription.
        if ($IDS::Ruleset::Providers{$provider}{'requires_subscription'} eq "True") {
                # Grab the subscription code.
                my $subscription_code = &get_subscription_code($provider);

                # Add the subscription code to the download url.
                $url =~ s/\<subscription_code\>/$subscription_code/g;

        }

        # Abort and return "no url", if no url could be determined for the provider.
        return "no url" unless ($url);

        # Pass the requested URL to the downloader.
        my $request = HTTP::Request->new(GET => $url);

        # Generate temporary file name, located in the tempoary download directory and with a suffix of ".tmp".
        # The downloaded file will be stored there until some sanity checks are performed.
        my $tmp = File::Temp->new( SUFFIX => ".tmp", DIR => "$tmp_dl_directory/", UNLINK => 0 );
        my $tmpfile = $tmp->filename();

        # Call function to get the final path and filename for the downloaded file.
        my $dl_rulesfile = &_get_dl_rulesfile($provider);

        # Check if the rulesfile already exits, because it has been downloaded in the past.
        #
        # In this case we are requesting the server if the remote file has been changed or not.
        # This will be done by sending the modification time in a special HTTP header.
        if (-f $dl_rulesfile) {
                # Call stat on the file.
                my $stat = stat($dl_rulesfile);

                # Omit the mtime of the existing file.
                my $mtime = $stat->mtime;

                # Convert the timestamp into right format.
                my $http_date = time2str($mtime);

                # Add the If-Modified-Since header to the request to ask the server if the
                # file has been modified.
                $request->header( 'If-Modified-Since' => "$http_date" );
        }

        # Read-in Etags file for known Etags if the file is present.
        my %etags = ();
        &General::readhash("$etags_file", \%etags) if (-f $etags_file);

        # Check if an Etag for the current provider is stored.
        if ($etags{$provider}) {
                # Grab the stored tag.
                my $etag = $etags{$provider};

                # Add an "If-None-Match header to the request to ask the server if the
                # file has been modified.
                $request->header( 'If-None-Match' => $etag );
        }

        my $dl_attempt = 1;
        my $response;

        # Download and retry on failure.
        while ($dl_attempt <= $max_dl_attempts) {
                # Perform the request and save the output into the tmpfile.
                $response = $downloader->request($request, $tmpfile);

                # Check if the download was successfull.
                if($response->is_success) {
                        # Break loop.
                        last;

                # Check if the server responds with 304 (Not Modified).
                } elsif ($response->code == 304) {
                        # Remove temporary file, if one exists.
                        unlink("$tmpfile") if (-e "$tmpfile");

                        # Return "not modified".
                        return "not modified";

                # Check if we ran out of download re-tries.
                } elsif ($dl_attempt eq $max_dl_attempts) {
                        # Obtain error.
                        my $error = $response->content;

                        # Remove temporary file, if one exists.
                        unlink("$tmpfile") if (-e "$tmpfile");

                        # Return the error message from response..
                        return "$error";
                }

                # Remove temporary file, if one exists.
                unlink("$tmpfile") if (-e "$tmpfile");

                # Increase download attempt counter.
                $dl_attempt++;
        }

        # Obtain the connection headers.
        my $headers = $response->headers;

        # Get the timestamp from header, when the file has been modified the
        # last time.
        my $last_modified = $headers->last_modified;

        # Get the remote size of the downloaded file.
        my $remote_filesize = $headers->content_length;

        # Grab the Etag from response it the server provides one.
        if ($response->header('Etag')) {
                # Add the Etag to the etags hash.
                $etags{$provider} = $response->header('Etag');

                # Write the etags file.
                &General::writehash($etags_file, \%etags);
        }

        # Perform stat on the tmpfile.
        my $stat = stat($tmpfile);

        # Grab the local filesize of the downloaded tarball.
        my $local_filesize = $stat->size;

        # Check if both file sizes match.
        if (($remote_filesize) && ($remote_filesize ne $local_filesize)) {
                # Delete temporary file.
                unlink("$tmpfile");

                # Return "1" - false.
                return "incomplete download";
        }

        # Overwrite the may existing rulefile or tarball with the downloaded one.
        move("$tmpfile", "$dl_rulesfile");

        # Check if we got a last-modified value from the server.
        if ($last_modified) {
                # Assign the last-modified timestamp as mtime to the
                # rules file.
                utime(time(), "$last_modified", "$dl_rulesfile");
        }

        # Delete temporary file.
        unlink("$tmpfile");

        # Set correct ownership for the tarball.
        set_ownership("$dl_rulesfile");

        # If we got here, everything worked fine. Return nothing.
        return;
}

#
## Function to extract a given ruleset.
##
## In case the ruleset provider offers a plain file, it simply will
## be copied.
#
sub extractruleset ($) {
        my ($provider) = @_;

        # Get full path and downloaded rulesfile for the given provider.
        my $tarball = &_get_dl_rulesfile($provider);

        # Check if the file exists.
        unless (-f $tarball) {
                &_log_to_syslog("Could not find ruleset file: $tarball");

                # Return nothing.
                return;
        }

        # Check if the temporary directories exist, otherwise create them.
        mkdir("$tmp_directory") unless (-d "$tmp_directory");
        mkdir("$tmp_rules_directory") unless (-d "$tmp_rules_directory");
        mkdir("$tmp_conf_directory") unless (-d "$tmp_conf_directory");

        # Omit the type (dl_type) of the stored ruleset.
        my $type = $IDS::Ruleset::Providers{$provider}{'dl_type'};

        # Handle the different ruleset types.
        if ($type eq "plain") {
                # Generate destination filename an full path.
                my $destination = "$tmp_rules_directory/$provider\-ruleset.rules";

                # Copy the file into the temporary rules directory.
                copy($tarball, $destination);

        } elsif ( $type eq "archive") {
                # Initialize the tar module.
                my $tar = Archive::Peek::Libarchive->new(filename => $tarball);

                # Loop through the archive
                $tar->iterate( sub {
                        my ($packed_file, $content) = @_;
                        my $destination;

                        # Splitt the packed file into chunks.
                        my $file = fileparse($packed_file);

                        # Handle msg-id.map file.
                        if ("$file" eq "sid-msg.map") {
                                # Set extract destination to temporary config_dir.
                                $destination = "$tmp_conf_directory/$provider\-sid-msg.map";

                        # Handle classification.conf
                        } elsif ("$file" eq "classification.config") {
                                # Set extract destination to temporary config_dir.
                                $destination = "$tmp_conf_directory/$provider\-classification.config";

                        # Handle rules files.
                        } elsif ($file =~ m/\.rules$/) {
                                # Skip rule files which are not located in the rules directory or archive root.
                                return unless(($packed_file =~ /^rules\//) || ($packed_file =~ /^$provider-rules\//) || ($packed_file !~ /\//));

                                # Skip deleted.rules.
                                #
                                # Mostly they have been taken out for correctness or performance reasons and therfore
                                # it is not a great idea to enable any of them.
                                return if($file =~ m/deleted.rules$/);

                                my $rulesfilename;

                                # Splitt the filename into chunks.
                                my @filename = split("-", $file);

                                # Reverse the array.
                                @filename = reverse(@filename);

                                # Get the amount of elements in the array.
                                my $elements = @filename;

                                # Remove last element of the hash.
                                # It contains the vendor name, which will be replaced.
                                if ($elements >= 3) {
                                # Remove last element from hash.
                                        pop(@filename);
                                }

                                # Check if the last element of the filename does not
                                # contain the providers name.
                                if ($filename[-1] ne "$provider") {
                                        # Add provider name as last element.
                                        push(@filename, $provider);
                                }

                                # Reverse the array back.
                                @filename = reverse(@filename);

                                # Generate the name for the rulesfile.
                                $rulesfilename = join("-", @filename);

                                # Set extract destination to temporaray rules_dir.
                                $destination = "$tmp_rules_directory/$rulesfilename";
                        } else {
                                # Skip all other files.
                                return;
                        }

                        # Check if the destination file exists.
                        unless(-e "$destination") {
                                # Open filehandle to write the content to a new file.
                                open(FILE, ">", "$destination") or die "Could not open $destination. $!\n";
                        } else {
                                # Open filehandle to append the content to the existing file.
                                open(FILE, ">>", "$destination") or die "Could not open $destination. $!\n";
                        }

                        # Write the extracted file content to the filehandle.
                        print FILE "$content" if ($content);

                        # Close the file handle.
                        close(FILE);
                });
        }
}

#
## A wrapper function to call the oinkmaster script, setup the rules structues and
## call the functions to merge the additional config files. (classification, sid-msg, etc.).
#
sub oinkmaster () {
        # Check if the files in rulesdir have the correct permissions.
        &_check_rulesdir_permissions();

        # Cleanup the rules directory before filling it with the new rulests.
        &_cleanup_rulesdir();

        # Get all enabled providers.
        my @enabled_providers = &get_enabled_providers();

        # Loop through the array of enabled providers.
        foreach my $provider (@enabled_providers) {
                # Call the extractruleset function.
                &extractruleset($provider);
        }

        # Call function to process the ruleset and do all modifications.
        &process_ruleset(@enabled_providers);

        # Call function to merge the classification files.
        &merge_classifications(@enabled_providers);

        # Call function to merge the sid to message mapping files.
        &merge_sid_msg(@enabled_providers);

        # Cleanup temporary directory.
        &cleanup_tmp_directory();
}

#
## Function to alter the ruleset.
#
sub process_ruleset(@) {
        my (@providers) = @_;

        # Hash to store the configured provider modes.
        my %providers_mode = &get_providers_mode();

        # Array to store the extracted rulefile from the temporary rules directory.
        my @extracted_rulefiles;

        # Get names of the extracted raw rulefiles.
        opendir(DIR, $tmp_rules_directory) or die "Could not read from $tmp_rules_directory. $!\n";
        while (my $file = readdir(DIR)) {
                # Ignore single and double dotted files.
                next if $file =~ /^\.\.?$/;

                # Add file to the array of extracted files.
                push(@extracted_rulefiles, $file);
        }

        # Close directory handle.
        closedir(DIR);

        # Loop through the array of providers.
        foreach my $provider (@providers) {
                # Hash to store the obtained SIDs and REV of each provider.
                my %rules = ();

                # Hash which holds modifications to apply to the rules.
                my %modifications = ();

                # Loop through the array of extraced rulefiles.
                foreach my $file (@extracted_rulefiles) {
                        # Skip file if it does not belong to the current processed provider.
                        next unless ($file =~ m/^$provider/);

                        # Open the rulefile.
                        open(FILE, "$tmp_rules_directory/$file") or die "Could not read $tmp_rules_directory/$file. $!\n";

                        # Loop through the file content.
                        while (my $line = <FILE>) {
                                # Skip blank  lines.
                                next if ($line =~ /^\s*$/);

                                # Call function to get the sid and rev of the rule.
                                my ($sid, $rev) = &_get_sid_and_rev($line);

                                # Skip rule if a sid with a higher rev already has added to the rules hash.
                                next if ($rev le $rules{$sid});

                                # Add the new or rule with higher rev to the hash of rules.
                                $rules{$sid} = $rev;
                        }

                        # Close file handle.
                        close(FILE);
                }

                # Get filename which contains the ruleset modifications for this provider.
                my $modification_file = &get_provider_ruleset_modifications_file($provider);

                # Read file which holds the modifications of the ruleset for the current provider.
                &General::readhash($modification_file, \%modifications) if (-f $modification_file);

                # Loop again through the array of extracted rulesfiles.
                foreach my $file (@extracted_rulefiles) {
                        # Skip the file if it does not belong to the current provider.
                        next unless ($file =~ m/^$provider/);

                        # Open the rulefile for writing.
                        open(RULEFILE, ">", "$rulespath/$file") or die "Could not write to file $rulespath/$file. $!\n";

                        # Open the rulefile for reading.
                        open(TMP_RULEFILE, "$tmp_rules_directory/$file") or die "Could not read $tmp_rules_directory/$file. $!\n";

                        # Loop through the raw temporary rulefile.
                        while (my $line = <TMP_RULEFILE>) {
                                # Get the sid and rev of the rule.
                                my ($sid, $rev) = &_get_sid_and_rev($line);

                                # Check if the current rule is obsoleted by a newer one.
                                #
                                # In this case the rev number in the rules hash is higher than the current one.
                                next if ($rev lt $rules{$sid});

                                # Check if the rule should be enabled or disabled.
                                if ($modifications{$sid} eq "enabled") {
                                        # Drop the # at the start of the line.
                                        $line =~ s/^\#//;
                                } elsif ($modifications{$sid} eq "disabled") {
                                        # Add a # at the start of the line to disable the rule.
                                        $line = "#$line" unless ($line =~ /^#/);
                                }

                                # Check if the Provider is set so IPS mode.
                                if ($providers_mode{$provider} eq "IPS") {
                                        # Replacements for sourcefire rules.
                                        $line =~ s/^#\s*(?:alert|drop)(.+policy balanced-ips alert)/alert${1}/;
                                        $line =~ s/^#\s*(?:alert|drop)(.+policy balanced-ips drop)/drop${1}/;

                                        # Replacements for generic rules.
                                        $line =~ s/^(#?)\s*(?:alert|drop)/${1}drop/;
                                        $line =~ s/^(#?)\s*drop(.+flowbits:noalert;)/${1}alert${2}/;
                                }

                                # Write line / rule to the target rule file.
                                print RULEFILE "$line";
                        }

                        # Close filehandles.
                        close(RULEFILE);
                        close(TMP_RULEFILE);
                }
        }
}

#
## Function to merge the classifications for a given amount of providers and write them
## to the classifications file.
#
sub merge_classifications(@) {
        my @providers = @_;

        # Hash to store all collected classifications.
        my %classifications = ();

        # Loop through the given array of providers.
        foreach my $provider (@providers) {
                # Generate full path to classification file.
                my $classification_file = "$tmp_conf_directory/$provider\-classification.config";

                # Skip provider if no classification file exists.
                next unless (-f "$classification_file");

                # Open the classification file.
                open(CLASSIFICATION, $classification_file) or die "Could not open file $classification_file. $!\n";

                # Loop through the file content.
                while(<CLASSIFICATION>) {
                        # Parse the file and grab the classification details.
                        if ($_ =~/.*config classification\: (.*)/) {
                                # Split the grabbed details.
                                my ($short_name, $short_desc, $priority) = split("\,", $1);

                                # Check if the grabbed classification is allready known and the priority value is greater
                                # than the stored one (which causes less priority in the IDS).
                                if (($classifications{$short_name}) && ($classifications{$short_name}[1] >= $priority)) {
                                        #Change the priority value to the stricter one.
                                        $classifications{$short_name} = [ "$classifications{$short_name}[0]", "$priority" ];
                                } else {
                                        # Add the classification to the hash.
                                        $classifications{$short_name} = [ "$short_desc", "$priority" ];
                                }
                        }
                }

                # Close the file.
                close(CLASSIFICATION);
        }

        # Open classification file for writing.
        open(FILE, ">", "$classification_file") or die "Could not write to $classification_file. $!\n";

        # Print notice about autogenerated file.
        print FILE "#Autogenerated file. Any custom changes will be overwritten!\n\n";

        # Sort and loop through the hash of classifications.
        foreach my $key (sort keys %classifications) {
                # Assign some nice variable names for the items.
                my $short_name = $key;
                my $short_desc = $classifications{$key}[0];
                my $priority = $classifications{$key}[1];

                # Write the classification to the file.
                print FILE "config classification: $short_name,$short_desc,$priority\n";
        }

        # Close file handle.
        close(FILE);
}

#
## Function to merge the "sid to message mapping" files of various given providers.
#
sub merge_sid_msg (@) {
        my @providers = @_;

        # Hash which contains all the sid to message mappings.
        my %mappings = ();

        # Loop through the array of given providers.
        foreach my $provider (@providers) {
                # Generate full path and filename.
                my $sid_msg_file = "$tmp_conf_directory/$provider\-sid-msg.map";

                # Skip provider if no sid to msg mapping file for this provider exists.
                next unless (-f $sid_msg_file);

                # Open the file.
                open(MAPPING, $sid_msg_file) or die "Could not open $sid_msg_file. $!\n";

                # Loop through the file content.
                while (<MAPPING>) {
                        # Remove newlines.
                        chomp($_);

                        # Skip lines which do not start with a number,
                        next unless ($_ =~ /^\d+/);

                        # Split line content and assign it to an array.
                        my @line = split(/ \|\| /, $_);

                        # Grab the first element (and remove it) from the line array.
                        # It contains the sid.
                        my $sid = shift(@line);

                        # Store the grabbed sid and the remain array as hash value.
                        # It still contains the messages, references etc.
                        $mappings{$sid} = [@line];
                }

                # Close file handle.
                close(MAPPING);
        }

        # Open mappings file for writing.
        open(FILE, ">", $sid_msg_file) or die "Could not write $sid_msg_file. $!\n";

        # Write notice about autogenerated file.
        print FILE "#Autogenerated file. Any custom changes will be overwritten!\n\n";

        # Loop through the hash of mappings.
        foreach my $sid ( sort keys %mappings) {
                # Grab data for the sid.
                my @data = @{$mappings{$sid}};

                # Add the sid to the data array.
                unshift(@data, $sid);

                # Generate line.
                my $line = join(" \|\| ", @data);

                print FILE "$line\n";

        }

        # Close file handle.
        close(FILE);
}

#
## A very tiny function to move an extracted ruleset from the temporary directory into
## the rules directory.
#
sub move_tmp_ruleset() {
        # Do a directory listing of the temporary directory.
        opendir  DH, $tmp_rules_directory;

        # Loop over all files.
        while(my $file = readdir DH) {
                # Move them to the rules directory.
                move "$tmp_rules_directory/$file" , "$rulespath/$file";
        }

        # Close directory handle.
        closedir DH;
}

#
## Function to cleanup the temporary IDS directroy.
#
sub cleanup_tmp_directory () {

        # Delete temporary directory and all containing files.
        rmtree([ "$tmp_directory" ]);
}

#
## Function to do all the logging stuff if the downloading or updating of the ruleset fails.
#
sub log_error ($) {
        my ($error) = @_;

        # Remove any newline.
        chomp($error);

        # Call private function to log the error message to syslog.
        &_log_to_syslog($error);

        # Call private function to write/store the error message in the storederrorfile.
        &_store_error_message($error);
}

#
## Function to log a given error message to the kernel syslog.
#
sub _log_to_syslog ($) {
        my ($message) = @_;

        # The syslog function works best with an array based input,
        # so generate one before passing the message details to syslog.
        my @syslog = ("ERR", "<ERROR> $message");

        # Establish the connection to the syslog service.
        openlog('oinkmaster', 'cons,pid', 'user');

        # Send the log message.
        syslog(@syslog);

        # Close the log handle.
        closelog();
}

#
## Private function to write a given error message to the storederror file.
#
sub _store_error_message ($) {
        my ($message) = @_;

        # Remove any newline.
        chomp($message);

        # Open file for writing.
        open (ERRORFILE, ">$storederrorfile") or die "Could not write to $storederrorfile. $!\n";

        # Write error to file.
        print ERRORFILE "$message\n";

        # Close file.
        close (ERRORFILE);

        # Set correct ownership for the file.
        &set_ownership("$storederrorfile");
}

#
## Private function to get the path and filename for a downloaded ruleset by a given provider.
#
sub _get_dl_rulesfile($) {
        my ($provider) = @_;

        # Abort if the requested provider is not known.
        return unless($IDS::Ruleset::Providers{$provider});

        # Try to gather the download type for the given provider.
        my $dl_type = $IDS::Ruleset::Providers{$provider}{'dl_type'};

        # Check if a download type could be grabbed.
        if ($dl_type) {
                # Obtain the file suffix for the download file type.
                my $suffix = $dl_type_to_suffix{$dl_type};

                # Check if a suffix has been found.
                unless ($suffix) {
                        # Abort return - nothing.
                        return;
                }

                # Generate the full filename and path for the stored rules file.
                my $rulesfile = "$dl_rules_path/$dl_rulesfile_prefix-$provider$suffix";

                # Return the generated filename.
                return $rulesfile;

        } else {
                # A downloaded ruleset for a provider which is not supported anymore is requested.
                #
                # Try to enumerate the downloaded ruleset file.
                foreach my $dl_type (keys %dl_type_to_suffix) {
                        # Get the file suffix for the supported type.
                        my $suffix = $dl_type_to_suffix{$dl_type};

                        # Generate possible ruleset file name.
                        my $rulesfile = "$dl_rules_path/$dl_rulesfile_prefix-$provider$suffix";

                        # Check if such a file exists.
                        if (-f $rulesfile) {
                                # Downloaded rulesfile found - Return the filename.
                                return $rulesfile;
                        }
                }
        }

        # If we got here, no rulesfile could be determined - return nothing.
        return;
}

#
## Private function to obtain the sid and rev of a rule.
#
## Returns an array with the sid as first and the rev as second value.
#
sub _get_sid_and_rev ($) {
        my ($line) = @_;

        my @ret;

        # Use regex to obtain the sid and rev.
        if ($line =~ m/.*sid:\s*(.*?);.*rev:\s*(.*?);/) {
                # Add the sid and rev to the array.
                push(@ret, $1);
                push(@ret, $2);
        }

        # Return the array.
        return @ret;
}

#
## Tiny function to delete the stored ruleset file or tarball for a given provider.
#
sub drop_dl_rulesfile ($) {
        my ($provider) = @_;

        # Gather the full path and name of the stored rulesfile.
        my $rulesfile = &_get_dl_rulesfile($provider);

        # Check if the given rulesfile exists.
        if (-f $rulesfile) {
                # Delete the stored rulesfile.
                unlink($rulesfile) or die "Could not delete $rulesfile. $!\n";
        }
}

#
## Function to check if the IDS is running.
#
sub ids_is_running () {
        if(-f $idspidfile) {
                # Open PID file for reading.
                open(PIDFILE, "$idspidfile") or die "Could not open $idspidfile. $!\n";

                # Grab the process-id.
                my $pid = <PIDFILE>;

                # Close filehandle.
                close(PIDFILE);

                # Remove any newline.
                chomp($pid);

                # Check if a directory for the process-id exists in proc.
                if(-d "/proc/$pid") {
                        # The IDS daemon is running return the process id.
                        return $pid;
                }
        }

        # Return nothing - IDS is not running.
        return;
}

#
## Function to call suricatactrl binary with a given command.
#
sub call_suricatactrl ($) {
        # Get called option.
        my ($option, $interval) = @_;

        # Loop through the array of supported commands and check if
        # the given one is part of it.
        foreach my $cmd (@suricatactrl_cmds) {
                # Skip current command unless the given one has been found.
                next unless($cmd eq $option);

                # Call the suricatactrl binary and pass the requrested
                # option to it.
                &General::system("$suricatactrl", "$option");

                # Return "1" - True.
                return 1;
        }

        # Command not found - return nothing.
        return;
}

#
## Function to create a new empty file.
#
sub create_empty_file($) {
        my ($file) = @_;

        # Check if the given file exists.
        if(-e $file) {
                # Do nothing to prevent from overwriting existing files.
                return;
        }

        # Open the file for writing.
        open(FILE, ">$file") or die "Could not write to $file. $!\n";

        # Close file handle.
        close(FILE);

        # Return true.
        return 1;
}

#
## Private function to check if the file permission of the rulespath are correct.
## If not, call suricatactrl to fix them.
#
sub _check_rulesdir_permissions() {
        # Check if the rulepath main directory is writable.
        unless (-W $rulespath) {
                # If not call suricatctrl to fix it.
                &call_suricatactrl("fix-rules-dir");
        }

        # Open snort rules directory and do a directory listing.
        opendir(DIR, $rulespath) or die $!;
        # Loop through the direcory.
        while (my $file = readdir(DIR)) {
                # We only want files.
                next unless (-f "$rulespath/$file");

                # Check if the file is writable by the user.
                if (-W "$rulespath/$file") {
                        # Everything is okay - go on to the next file.
                        next;
                } else {
                        # There are wrong permissions, call suricatactrl to fix it.
                        &call_suricatactrl("fix-rules-dir");
                }
        }
}

#
## Private function to cleanup the directory which contains
## the IDS rules, before extracting and modifing the new ruleset.
#
sub _cleanup_rulesdir() {
        # Open rules directory and do a directory listing.
        opendir(DIR, $rulespath) or die $!;

        # Loop through the direcory.
        while (my $file = readdir(DIR)) {
                # We only want files.
                next unless (-f "$rulespath/$file");

                # Skip rules file for whitelisted hosts.
                next if ("$rulespath/$file" eq $whitelist_file);

                # Skip rules file with local rules.
                next if ("$rulespath/$file" eq $local_rules_file);

                # Delete the current processed file, if not, exit this function
                # and return an error message.
                unlink("$rulespath/$file") or return "Could not delete $rulespath/$file. $!\n";
        }

        # Return nothing;
        return;
}

#
## Function to generate the file which contains the home net information.
#
sub generate_home_net_file() {
        my %netsettings;

        # Read-in network settings.
        &General::readhash("${General::swroot}/ethernet/settings", \%netsettings);

        # Get available network zones.
        my @network_zones = &Network::get_available_network_zones();

        # Temporary array to store network address and prefix of the configured
        # networks.
        my @networks;

        # Loop through the array of available network zones.
        foreach my $zone (@network_zones) {
                # Check if the current processed zone is red.
                if($zone eq "red") {
                        # Grab the IP-address of the red interface.
                        my $red_address = &get_red_address();

                        # Check if an address has been obtained.
                        if ($red_address) {
                                # Generate full network string.
                                my $red_network = join("/", $red_address, "32");

                                # Add the red network to the array of networks.
                                push(@networks, $red_network);
                        }

                        # Check if the configured RED_TYPE is static.
                        if ($netsettings{'RED_TYPE'} eq "STATIC") {
                                # Get configured and enabled aliases.
                                my @aliases = &get_aliases();

                                # Loop through the array.
                                foreach my $alias (@aliases) {
                                        # Add "/32" prefix.
                                        my $network = join("/", $alias, "32");

                                        # Add the generated network to the array of networks.
                                        push(@networks, $network);
                                }
                        }
                # Process remaining network zones.
                } else {
                        # Convert current zone name into upper case.
                        $zone = uc($zone);

                        # Generate key to access the required data from the netsettings hash.
                        my $zone_netaddress = $zone . "_NETADDRESS";
                        my $zone_netmask = $zone . "_NETMASK";

                        # Obtain the settings from the netsettings hash.
                        my $netaddress = $netsettings{$zone_netaddress};
                        my $netmask = $netsettings{$zone_netmask};

                        # Convert the subnetmask into prefix notation.
                        my $prefix = &Network::convert_netmask2prefix($netmask);

                        # Generate full network string.
                        my $network = join("/", $netaddress,$prefix);

                        # Check if the network is valid.
                        if(&Network::check_subnet($network)) {
                                # Add the generated network to the array of networks.
                                push(@networks, $network);
                        }
                }
        }

        # Format home net declaration.
        my $line = "\"[" . join(',', @networks) . "]\"";

        # Open file to store the addresses of the home net.
        open(FILE, ">$homenet_file") or die "Could not open $homenet_file. $!\n";

        # Print yaml header.
        print FILE "%YAML 1.1\n";
        print FILE "---\n\n";

        # Print notice about autogenerated file.
        print FILE "#Autogenerated file. Any custom changes will be overwritten!\n";

        # Print the generated and required HOME_NET declaration to the file.
        print FILE "HOME_NET:\t$line\n";

        # Close file handle.
        close(FILE);
}

#
# Function to generate and write the file which contains the configured and used DNS servers.
#
sub generate_dns_servers_file() {
        # Get the used DNS servers.
        my @nameservers = &General::get_nameservers();

        # Get network settings.
        my %netsettings;
        &General::readhash("${General::swroot}/ethernet/settings", \%netsettings);

        # Format dns servers declaration.
        my $line = "";

        # Check if the system has configured nameservers.
        if (@nameservers) {
                # Add the GREEN address as DNS servers.
                push(@nameservers, $netsettings{'GREEN_ADDRESS'});

                # Check if a BLUE zone exists.
                if ($netsettings{'BLUE_ADDRESS'}) {
                        # Add the BLUE address to the array of nameservers.
                        push(@nameservers, $netsettings{'BLUE_ADDRESS'});
                }

                # Generate the line which will be written to the DNS servers file.
                $line = join(",", @nameservers);
        } else {
                # External net simply contains (any).
                $line = "\$EXTERNAL_NET";
        }

        # Open file to store the used DNS server addresses.
        open(FILE, ">$dns_servers_file") or die "Could not open $dns_servers_file. $!\n";

        # Print yaml header.
        print FILE "%YAML 1.1\n";
        print FILE "---\n\n";

        # Print notice about autogenerated file.
        print FILE "#Autogenerated file. Any custom changes will be overwritten!\n";

        # Print the generated DNS declaration to the file.
        print FILE "DNS_SERVERS:\t\"[$line]\"\n";

        # Close file handle.
        close(FILE);
}

#
# Function to generate and write the file which contains the HTTP_PORTS definition.
#
sub generate_http_ports_file() {
        my %proxysettings;

        # Read-in proxy settings
        &General::readhash("${General::swroot}/proxy/advanced/settings", \%proxysettings);

        # Check if the proxy is enabled.
        if (( -e "${General::swroot}/proxy/enable") || (-e "${General::swroot}/proxy/enable_blue")) {
                # Add the proxy port to the array of HTTP ports.
                push(@http_ports, $proxysettings{'PROXY_PORT'});
        }

        # Check if the transparent mode of the proxy is enabled.
        if ((-e "${General::swroot}/proxy/transparent") || (-e "${General::swroot}/proxy/transparent_blue")) {
                # Add the transparent proxy port to the array of HTTP ports.
                push(@http_ports, $proxysettings{'TRANSPARENT_PORT'});
        }

        # Format HTTP_PORTS declaration.
        my $line = "";

        # Generate line which will be written to the http ports file.
        $line = join(",", @http_ports);

        # Open file to store the HTTP_PORTS.
        open(FILE, ">$http_ports_file") or die "Could not open $http_ports_file. $!\n";

        # Print yaml header.
        print FILE "%YAML 1.1\n";
        print FILE "---\n\n";

        # Print notice about autogenerated file.
        print FILE "#Autogenerated file. Any custom changes will be overwritten!\n";

        # Print the generated HTTP_PORTS declaration to the file.
        print FILE "HTTP_PORTS:\t\"[$line]\"\n";

        # Close file handle.
        close(FILE);
}

#
## Function to write the file that contains the rulefiles which are loaded by suricaa.
##
## This function requires an array of used provider handles.
#
sub write_used_rulefiles_file (@) {
        my (@providers) = @_;

        # Get the enabled application layer protocols.
        my @enabled_app_layer_protos = &get_suricata_enabled_app_layer_protos();

        # Open the file.
        open (FILE, ">", $suricata_used_rulesfiles_file) or die "Could not write to $suricata_used_rulesfiles_file. $!\n";

        print FILE "%YAML 1.1\n";
        print FILE "---\n\n";

        # Write notice about autogenerated file.
        print FILE "#Autogenerated file. Any custom changes will be overwritten!\n";

        # Loop through the array of static included rulesfiles.
        foreach my $file (@static_included_rulefiles) {
                # Check if the file exists.
                if (-f "$rulespath/$file") {
                        # Write the rulesfile name to the file.
                        print FILE " - $rulespath/$file\n";
                }
        }

        print FILE "\n#Default rules for used application layer protocols.\n";
        foreach my $enabled_app_layer_proto (@enabled_app_layer_protos) {
                # Check if the current processed app layer proto needs to be translated
                # into an application name.
                if (exists($tr_app_layer_proto{$enabled_app_layer_proto})) {
                        # Obtain the translated application name for this protocol.
                        $enabled_app_layer_proto = $tr_app_layer_proto{$enabled_app_layer_proto};
                }

                # Generate filename.
                my $rulesfile = "$default_rulespath/$enabled_app_layer_proto\.rules";

                # Check if such a file exists.
                if (-f "$rulesfile") {
                        # Write the rulesfile name to the file.
                        print FILE " - $rulesfile\n";
                }

                # Generate filename with "events" in filename.
                $rulesfile = "$default_rulespath/$enabled_app_layer_proto\-events.rules";

                # Check if this file exists.
                if (-f "$rulesfile" ) {
                        # Write the rulesfile name to the file.
                        print FILE " - $rulesfile\n";
                }
        }

        # Loop through the array of enabled providers.
        foreach my $provider (@providers) {
                # Skip unsupported providers.
                next unless ($IDS::Ruleset::Providers{$provider});

                # Get the used rulefile for this provider.
                my @used_rulesfiles = &get_provider_used_rulesfiles($provider);

                # Check if there are
                if(@used_rulesfiles) {
                        # Add notice to the file.
                        print FILE "\n#Used Rulesfiles for provider $provider.\n";

                        # Loop through the array of used rulefiles.
                        foreach my $enabled_rulesfile (@used_rulesfiles) {
                                # Generate name and full path to the rulesfile.
                                my $rulesfile = "$rulespath/$enabled_rulesfile";

                                # Write the ruelsfile name to the file.
                                print FILE " - $rulesfile\n";
                        }
                }
        }

        # Close the file handle
        close(FILE);
}

#
## Tiny function to generate the full path and name for the file which stores the used rulefiles of a given provider.
#
sub get_provider_used_rulesfiles_file ($) {
        my ($provider) = @_;

        my $filename = "$settingsdir/$provider\-used\-rulesfiles";

        # Return the gernerated file.
        return $filename;
}

#
## Tiny function to generate the full path and name for the file which stores the modifications of a ruleset.
#
sub get_provider_ruleset_modifications_file($) {
        my ($provider) = @_;

        my $filename = "$settingsdir/$provider\-modifications";

        # Return the filename.
        return $filename;
}

#
## Function to get the subscription code of a configured provider.
#
sub get_subscription_code($) {
        my ($provider) = @_;

        my %configured_providers = ();

        # Read-in providers settings file.
        &General::readhasharray($providers_settings_file, \%configured_providers);

        # Loop through the hash of configured providers.
        foreach my $id (keys %configured_providers) {
                # Assign nice human-readable values to the data fields.
                my $provider_handle = $configured_providers{$id}[0];
                my $subscription_code = $configured_providers{$id}[1];

                # Check if the current processed provider is the requested one.
                if ($provider_handle eq $provider) {
                        # Return the obtained subscription code.
                        return $subscription_code;
                }
        }

        # No subscription code found - return nothing.
        return;
}

#
## Function to get the ruleset date for a given provider.
##
## The function simply return the creation date in a human read-able format
## of the stored providers rulesfile.
#
sub get_ruleset_date($) {
        my ($provider) = @_;
        my $date;
        my $mtime;

        # Get the stored rulesfile for this provider.
        my $stored_rulesfile = &_get_dl_rulesfile($provider);

        # Check if we got a file.
        if (-f $stored_rulesfile) {
                # Call stat on the rulestarball.
                my $stat = stat("$stored_rulesfile");

                # Get timestamp the file creation.
                $mtime = $stat->mtime;
        }

        # Check if the timestamp has not been grabbed.
        unless ($mtime) {
                # Return N/A for Not available.
                return "N/A";
        }

        # Convert into human read-able format.
        $date = strftime('%Y-%m-%d %H:%M:%S', localtime($mtime));

        # Return the date.
        return $date;
}

#
## Function to gather the version of suricata.
#
sub get_suricata_version($) {
        my ($format) = @_;

        # Execute piped suricata command and return the version information.
        open(SURICATA, "suricata -V |") or die "Couldn't execute program: $!";

        # Grab and store the output of the piped program.
        my $version_string = <SURICATA>;

        # Close pipe.
        close(SURICATA);

        # Remove newlines.
        chomp($version_string);

        # Grab the version from the version string.
        $version_string =~ /([0-9]+([.][0-9]+)+)/;

        # Splitt the version into single chunks.
        my ($major_ver, $minor_ver, $patchlevel) = split(/\./, $1);

        # Check and return the requested version sheme.
        if ($format eq "major") {
                # Return the full version.
                return "$major_ver";
        } elsif ($format eq "minor") {
                # Return the major and minor part.
                return "$major_ver.$minor_ver";
        } else {
                # Return the full version string.
                return "$major_ver.$minor_ver.$patchlevel";
        }
}

#
## Function to get the enabled application layer protocols.
#
sub get_suricata_enabled_app_layer_protos() {
        # Array to store and return the enabled app layer protos.
        my @enabled_app_layer_protos = ();

        # Execute piped suricata command and return the list of
        # enabled application layer protocols.
        open(SURICATA, "suricata --list-app-layer-protos |") or die "Could not execute program: $!";

        # Grab and store the list of enabled application layer protocols.
        my @output = <SURICATA>;

        # Close pipe.
        close(SURICATA);

        # Merge allways enabled static application layers protocols array.
        @enabled_app_layer_protos = @static_enabled_app_layer_protos;

        # Loop through the array which contains the output of suricata.
        foreach my $line (@output) {
                # Skip header line which starts with "===".
                next if ($line =~ /^\s*=/);

                # Skip info or warning lines.
                next if ($line =~ /\s*--/);

                # Remove newlines.
                chomp($line);

                # Add enabled app layer proto to the array.
                push(@enabled_app_layer_protos, $line);
        }

        # Sort the array.
        @enabled_app_layer_protos = sort(@enabled_app_layer_protos);

        # Return the array.
        return @enabled_app_layer_protos;
}

#
## Function to generate the rules file with whitelisted addresses.
#
sub generate_ignore_file() {
        my %ignored = ();

        # SID range 1000000-1999999 Reserved for Local Use
        # Put your custom rules in this range to avoid conflicts
        my $sid = 1500000;

        # Read-in ignoredfile.
        &General::readhasharray($IDS::ignored_file, \%ignored);

        # Open ignorefile for writing.
        open(FILE, ">$IDS::whitelist_file") or die "Could not write to $IDS::whitelist_file. $!\n";

        # Config file header.
        print FILE "# Autogenerated file.\n";
        print FILE "# All user modifications will be overwritten.\n\n";

        # Add all user defined addresses to the whitelist.
        #
        # Check if the hash contains any elements.
        if (keys (%ignored)) {
                # Loop through the entire hash and write the host/network
                # and remark to the ignore file.
                while ( (my $key) = each %ignored) {
                        my $address = $ignored{$key}[0];
                        my $remark = $ignored{$key}[1];
                        my $status = $ignored{$key}[2];

                        # Check if the status of the entry is "enabled".
                        if ($status eq "enabled") {
                                # Check if the address/network is valid.
                                if ((&General::validip($address)) || (&General::validipandmask($address))) {
                                        # Write rule line to the file to pass any traffic from this IP
                                        print FILE "pass ip $address any -> any any (msg:\"pass all traffic from/to $address\"\; bypass; sid:$sid\;)\n";

                                        # Increment sid.
                                        $sid++;
                                }
                        }
                }
        }

        close(FILE);
}

#
## Function to set correct ownership for single files and directories.
#

sub set_ownership($) {
        my ($target) = @_;

        # User and group of the WUI.
        my $uname = "nobody";
        my $grname = "nobody";

        # The chown function implemented in perl requies the user and group as nummeric id's.
        my $uid = getpwnam($uname);
        my $gid = getgrnam($grname);

        # Check if the given target exists.
        unless ($target) {
                # Stop the script and print error message.
                die "The $target does not exist. Cannot change the ownership!\n";
        }

        # Check weather the target is a file or directory.
        if (-f $target) {
                # Change ownership ot the single file.
                chown($uid, $gid, "$target");
        } elsif (-d $target) {
                # Do a directory listing.
                opendir(DIR, $target) or die $!;
                        # Loop through the direcory.
                        while (my $file = readdir(DIR)) {

                                # We only want files.
                                next unless (-f "$target/$file");

                                # Set correct ownership for the files.
                                chown($uid, $gid, "$target/$file");
                        }

                closedir(DIR);

                # Change ownership of the directory.
                chown($uid, $gid, "$target");
        }
}

#
## Function to read-in the aliases file and returns all configured and enabled aliases.
#
sub get_aliases() {
        # Location of the aliases file.
        my $aliases_file = "${General::swroot}/ethernet/aliases";

        # Array to store the aliases.
        my @aliases;

        # Check if the file is empty.
        if (-z $aliases_file) {
                # Abort nothing to do.
                return;
        }

        # Open the aliases file.
        open(ALIASES, $aliases_file) or die "Could not open $aliases_file. $!\n";

        # Loop through the file content.
        while (my $line = <ALIASES>) {
                # Remove newlines.
                chomp($line);

                # Splitt line content into single chunks.
                my ($address, $state, $remark) = split(/\,/, $line);

                # Check if the state of the current processed alias is "on".
                if ($state eq "on") {
                        # Check if the address is valid.
                        if(&Network::check_ip_address($address)) {
                                # Add the alias to the array of aliases.
                                push(@aliases, $address);
                        }
                }
        }

        # Close file handle.
        close(ALIASES);

        # Return the array.
        return @aliases;
}

#
## Function to grab the current assigned IP-address on red.
#
sub get_red_address() {
        # File, which contains the current IP-address of the red interface.
        my $file = "${General::swroot}/red/local-ipaddress";

        # Check if the file exists.
        if (-e $file) {
                # Open the given file.
                open(FILE, "$file") or die "Could not open $file.";

                # Obtain the address from the first line of the file.
                my $address = <FILE>;

                # Close filehandle
                close(FILE);

                # Remove newlines.
                chomp $address;

                # Check if the grabbed address is valid.
                if (&General::validip($address)) {
                        # Return the address.
                        return $address;
                }
        }

        # Return nothing.
        return;
}

#
## Function to get the used rules files of a given provider.
#
sub get_provider_used_rulesfiles($) {
        my ($provider) = @_;

        # Hash to store the used rulefiles of the provider.
        my %provider_rulefiles = ();

        # Array to store the used rulefiles.
        my @used_rulesfiles = ();

        # Get the filename which contains the used rulefiles for this provider.
        my $used_rulesfiles_file = &get_provider_used_rulesfiles_file($provider);

        # Read-in file, if it exists.
        &General::readhash("$used_rulesfiles_file", \%provider_rulefiles) if (-f $used_rulesfiles_file);

        # Loop through the hash of rulefiles which does the provider offer.
        foreach my $rulefile (keys %provider_rulefiles) {
                # Skip disabled rulefiles.
                next unless($provider_rulefiles{$rulefile} eq "enabled");

                # The General::readhash function does not allow dots as
                # key value and limits the key "string" to the part before
                # the dot, in case it contains one.
                #
                # So add the file extension for the rules file manually again.
                $rulefile = "$rulefile.rules";

                # Add the enabled rulefile to the array of enabled rulefiles.
                push(@used_rulesfiles, $rulefile);
        }

        # Return the array of used rulesfiles.
        return @used_rulesfiles;
}

#
## Function to delete the stored etag data of a given provider.
#
sub remove_from_etags ($) {
        my ($provider) = @_;

        my %etags;

        # Early exit function if the etags file does not exist.
        return unless (-f $etags_file);

        # Read-in etag file.
        &General::readhash("$etags_file", \%etags);

        # Check if the hash contains an entry for the given provider.
        if ($etags{$provider}) {
                # Drop the entry.
                delete($etags{$provider});

                # Write back the etags file.
                &General::writehash("$etags_file", \%etags);
        }
}

#
## Function to write the lock file for locking the WUI, while
## the autoupdate script runs.
#
sub lock_ids_page() {
        # Call subfunction to create the file.
        &create_empty_file($ids_page_lock_file);
}

#
## Function to release the lock of the WUI, again.
#
sub unlock_ids_page() {
        # Delete lock file.
        unlink($ids_page_lock_file);
}

1;