[people/pmueller/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>                    #
#                                                                          #
############################################################################

package IDS;

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

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

# File where the used rulefiles are stored.
our $used_rulefiles_file = "$settingsdir/suricata-used-rulefiles.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 contains the enabled sids.
our $enabled_sids_file = "$settingsdir/oinkmaster-enabled-sids.conf";

# File which contains the disabled sids.
our $disabled_sids_file = "$settingsdir/oinkmaster-disabled-sids.conf";

# File which contains wheater the rules should be changed.
our $modify_sids_file = "$settingsdir/oinkmaster-modify-sids.conf";

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

# File which stores the configured rules-settings.
our $rules_settings_file = "$settingsdir/rules-settings";

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

# Location and name of the tarball which contains the ruleset.
our $rulestarball = "/var/tmp/idsrules.tar.gz";

# 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 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";

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

# Array with supported cron intervals.
my @cron_intervals = ('off', 'daily', 'weekly' );

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

#
## 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 "$enabled_sids_file") { &create_empty_file($enabled_sids_file); }
        unless (-f "$disabled_sids_file") { &create_empty_file($disabled_sids_file); }
        unless (-f "$modify_sids_file") { &create_empty_file($modify_sids_file); }
        unless (-f "$used_rulefiles_file") { &create_empty_file($used_rulefiles_file); }
        unless (-f "$ids_settings_file") { &create_empty_file($ids_settings_file); }
        unless (-f "$rules_settings_file") { &create_empty_file($rules_settings_file); }
        unless (-f "$ignored_file") { &create_empty_file($ignored_file); }
        unless (-f "$whitelist_file" ) { &create_empty_file($whitelist_file); }
}

#
## 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) {
                                # Log error to syslog.
                                &_log_to_syslog("Not enough free disk space on /var. Only $available MB from 300 MB available.");

                                # Exit function and return "1" - False.
                                return 1;
                        }
                }
        }

        # Everything okay, return nothing.
        return;
}

#
## This function is responsible for downloading the configured IDS ruleset.
##
## * At first it obtains from the stored rules settings which ruleset should be downloaded.
## * The next step is to get the download locations for all available rulesets.
## * After that, the function will check if an upstream proxy should be used and grab the settings.
## * The last step will be to generate the final download url, by obtaining the URL for the desired
##   ruleset, add the settings for the upstream proxy and final grab the rules tarball from the server.
#
sub downloadruleset {
        # Get rules settings.
        my %rulessettings=();
        &General::readhash("$rules_settings_file", \%rulessettings);

        # Check if a ruleset has been configured.
        unless($rulessettings{'RULES'}) {
                # Log that no ruleset has been configured and abort.
                &_log_to_syslog("No ruleset source has been configured.");

                # Return "1".
                return 1;
        }

        # Get all available ruleset locations.
        my %rulesetsources=();
        &General::readhash($rulesetsourcesfile, \%rulesetsources);

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

        # Load required perl module to handle the download.
        use LWP::UserAgent;

        # Init the download module.
        my $downloader = LWP::UserAgent->new;

        # 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 right url based on the configured vendor.
        my $url = $rulesetsources{$rulessettings{'RULES'}};

        # Check if the vendor requires an oinkcode and add it if needed.
        $url =~ s/\<oinkcode\>/$rulessettings{'OINKCODE'}/g;

        # Abort if no url could be determined for the vendor.
        unless ($url) {
                # Log error and abort.
                &_log_to_syslog("Unable to gather a download URL for the selected ruleset.");
                return 1;
        }

        # Variable to store the filesize of the remote object.
        my $remote_filesize;

        # The sourcfire (snort rules) does not allow to send "HEAD" requests, so skip this check
        # for this webserver.
        #
        # Check if the ruleset source contains "snort.org".
        unless ($url =~ /\.snort\.org/) {
                # Pass the requrested url to the downloader.
                my $request = HTTP::Request->new(HEAD => $url);

                # Accept the html header.
                $request->header('Accept' => 'text/html');

                # Perform the request and fetch the html header.
                my $response = $downloader->request($request);

                # Check if there was any error.
                unless ($response->is_success) {
                        # Obtain error.
                        my $error = $response->status_line();

                        # Log error message.
                        &_log_to_syslog("Unable to download the ruleset. \($error\)");

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

                # Assign the fetched header object.
                my $header = $response->headers();

                # Grab the remote file size from the object and store it in the
                # variable.
                $remote_filesize = $header->content_length;
        }

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

        # Generate temporary file name, located in "/var/tmp" and with a suffix of ".tar.gz".
        my $tmp = File::Temp->new( SUFFIX => ".tar.gz", DIR => "/var/tmp/", UNLINK => 0 );
        my $tmpfile = $tmp->filename();

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

        # Perform the request and save the output into the tmpfile.
        my $response = $downloader->request($request, $tmpfile);

        # Check if there was any error.
        unless ($response->is_success) {
                # Obtain error.
                my $error = $response->content;

                # Log error message.
                &_log_to_syslog("Unable to download the ruleset. \($error\)");

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

        # Load perl stat module.
        use File::stat;

        # 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)) {
                # Log error message.
                &_log_to_syslog("Unable to completely download the ruleset. ");
                &_log_to_syslog("Only got $local_filesize Bytes instead of $remote_filesize Bytes. ");

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

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

        # Load file copy module, which contains the move() function.
        use File::Copy;

        # Overwrite existing rules tarball with the new downloaded one.
        move("$tmpfile", "$rulestarball");

        # Set correct ownership for the rulesdir and files.
        set_ownership("$rulestarball");

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

#
## A tiny wrapper function to call the oinkmaster script.
#
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 rulest.
        &_cleanup_rulesdir();

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

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

        # Call oinkmaster to generate ruleset.
        open(OINKMASTER, "/usr/local/bin/oinkmaster.pl -s -u file://$rulestarball -C $settingsdir/oinkmaster.conf -o $rulespath 2>&1 |") or die "Could not execute oinkmaster $!\n";

        # Log output of oinkmaster to syslog.
        while(<OINKMASTER>) {
                # The syslog function works best with an array based input,
                # so generate one before passing the message details to syslog.
                my @syslog = ("INFO", "$_");

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

        # Close the pipe to oinkmaster process.
        close(OINKMASTER);

        # Close the log handle.
        closelog();
}

#
## 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) = @_;

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

        # 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");
}

#
## 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);

                # Check if the given command is "cron".
                if ($option eq "cron") {
                        # Check if an interval has been given.
                        if ($interval) {
                                # Check if the given interval is valid.
                                foreach my $element (@cron_intervals) {
                                        # Skip current element until the given one has been found.
                                        next unless($element eq $interval);

                                        # Call the suricatactrl binary and pass the "cron" command
                                        # with the requrested interval.
                                        &General::system("$suricatactrl", "$option", "$interval");

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

                        # If we got here, the given interval is not supported or none has been given. - Return nothing.
                        return;
                } else {
                        # 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 element if it has config as file extension.
                next if ($file =~ m/\.config$/);

                # 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 generate and write the file for used rulefiles.
#
sub write_used_rulefiles_file(@) {
        my @files = @_;

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

        # Write yaml header to the file.
        print FILE "%YAML 1.1\n";
        print FILE "---\n\n";

        # Write header to file.
        print FILE "#Autogenerated file. Any custom changes will be overwritten!\n";

        # Allways use the whitelist.
        print FILE " - whitelist.rules\n";

        # Loop through the array of given files.
        foreach my $file (@files) {
                # Check if the given filename exists and write it to the file of used rulefiles.
                if(-f "$rulespath/$file") {
                        print FILE " - $file\n";
                }
        }

        # Close file after writing.
        close(FILE);
}

#
## Function to generate and write the file for modify the ruleset.
#
sub write_modify_sids_file() {
        # Get configured settings.
        my %idssettings=();
        my %rulessettings=();
        &General::readhash("$ids_settings_file", \%idssettings);
        &General::readhash("$rules_settings_file", \%rulessettings);

        # Gather the configured ruleset.
        my $ruleset = $rulessettings{'RULES'};

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

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

        # Check if the traffic only should be monitored.
        unless($idssettings{'MONITOR_TRAFFIC_ONLY'} eq 'on') {
                # Suricata is in IPS mode, which means that the rule actions have to be changed
                # from 'alert' to 'drop', however not all rules should be changed.  Some rules
                # exist purely to set a flowbit which is used to convey other information, such
                # as a specific type of file being downloaded, to other rulewhich then check for
                # malware in that file.  Rules which fall into the first category should stay as
                # alert since not all flows of that type contain malware.

                if($ruleset eq 'registered' or $ruleset eq 'subscripted' or $ruleset eq 'community') {
                        # These types of rulesfiles contain meta-data which gives the action that should
                        # be used when in IPS mode.  Do the following:
                        #
                        # 1. Disable all rules and set the action to 'drop'
                        # 2. Set the action back to 'alert' if the rule contains 'flowbits:noalert;'
                        #    This should give rules not in the policy a reasonable default if the user
                        #    manually enables them.
                        # 3. Enable rules and set actions according to the meta-data strings.

                        my $policy = 'balanced';  # Placeholder to allow policy to be changed.

                        print FILE <<END;
modifysid * "^#?(?:alert|drop)" | "#drop"
modifysid * "^#drop(.+flowbits:noalert;)" | "#alert\${1}"
modifysid * "^#(?:alert|drop)(.+policy $policy-ips alert)" | "alert\${1}"
modifysid * "^#(?:alert|drop)(.+policy $policy-ips drop)" | "drop\${1}"
END
                } else {
                        # These rulefiles don't have the metadata, so set rules to 'drop' unless they
                        # contain the string 'flowbits:noalert;'.
                        print FILE <<END;
modifysid * "^(#?)(?:alert|drop)" | "\${1}drop"
modifysid * "^(#?)drop(.+flowbits:noalert;)" | "\${1}alert\${2}"
END
                }
        }

        # Close file handle.
        close(FILE);
}

#
## 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 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 $address\"\; sid:$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 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;