use accept mark for security groups

[pve-firewall.git] / PVE / Firewall.pm

package PVE::Firewall;

use warnings;
use strict;
use Data::Dumper;
use Digest::SHA;
use PVE::Tools;
use PVE::QemuServer;
use File::Path;
use IO::File;
use Net::IP;
use PVE::Tools qw(run_command lock_file);

use Data::Dumper;

my $pve_fw_lock_filename = "/var/lock/pvefw.lck";

my $macros;

# todo: implement some kind of MACROS, like shorewall /usr/share/shorewall/macro.*
sub get_firewall_macros {

    return $macros if $macros;

    #foreach my $path (</usr/share/shorewall/macro.*>) {
    #  if ($path =~ m|/macro\.(\S+)$|) {
    #    $macros->{$1} = 1;
    #  }
    #}

    $macros = {}; # fixme: implemet me

    return $macros;
}

my $etc_services;

sub get_etc_services {

    return $etc_services if $etc_services;

    my $filename = "/etc/services";

    my $fh = IO::File->new($filename, O_RDONLY);
    if (!$fh) {
	warn "unable to read '$filename' - $!\n";
	return {};
    }

    my $services = {};

    while (my $line = <$fh>) {
	chomp ($line);
	next if $line =~m/^#/;
	next if ($line =~m/^\s*$/);

	if ($line =~ m!^(\S+)\s+(\S+)/(tcp|udp).*$!) {
	    $services->{byid}->{$2}->{name} = $1;
	    $services->{byid}->{$2}->{$3} = 1;
	    $services->{byname}->{$1} = $services->{byid}->{$2};
	}
    }

    close($fh);

    $etc_services = $services;    
    

    return $etc_services;
}

my $etc_protocols;

sub get_etc_protocols {
    return $etc_protocols if $etc_protocols;

    my $filename = "/etc/protocols";

    my $fh = IO::File->new($filename, O_RDONLY);
    if (!$fh) {
	warn "unable to read '$filename' - $!\n";
	return {};
    }

    my $protocols = {};

    while (my $line = <$fh>) {
	chomp ($line);
	next if $line =~m/^#/;
	next if ($line =~m/^\s*$/);

	if ($line =~ m!^(\S+)\s+(\d+)\s+.*$!) {
	    $protocols->{byid}->{$2}->{name} = $1;
	    $protocols->{byname}->{$1} = $protocols->{byid}->{$2};
	}
    }

    close($fh);

    $etc_protocols = $protocols;

    return $etc_protocols;
}

sub parse_address_list {
    my ($str) = @_;

    my $nbaor = 0;
    foreach my $aor (split(/,/, $str)) {
	if (!Net::IP->new($aor)) {
	    my $err = Net::IP::Error();
	    die "invalid IP address: $err\n";
	}else{
	    $nbaor++;
	}
    }
    return $nbaor;
}

sub parse_port_name_number_or_range {
    my ($str) = @_;

    my $services = PVE::Firewall::get_etc_services();
    my $nbports = 0;
    foreach my $item (split(/,/, $str)) {
	my $portlist = "";
	foreach my $pon (split(':', $item, 2)) {
	    if ($pon =~ m/^\d+$/){
		die "invalid port '$pon'\n" if $pon < 0 && $pon > 65536;
	    }else{
		die "invalid port $services->{byname}->{$pon}\n" if !$services->{byname}->{$pon};
	    }
	    $nbports++;
	}
    }

    return ($nbports);
}

my $bridge_firewall_enabled = 0;

sub enable_bridge_firewall {

    return if $bridge_firewall_enabled; # only once

    system("echo 1 > /proc/sys/net/bridge/bridge-nf-call-iptables");
    system("echo 1 > /proc/sys/net/bridge/bridge-nf-call-ip6tables");

    $bridge_firewall_enabled = 1;
}

my $rule_format = "%-15s %-30s %-30s %-15s %-15s %-15s\n";

sub iptables {
    my ($cmd) = @_;

    run_command("/sbin/iptables $cmd", outfunc => sub {}, errfunc => sub {});
}

sub iptables_restore_cmdlist {
    my ($cmdlist) = @_;

    run_command("/sbin/iptables-restore -n", input => $cmdlist);
}

sub iptables_get_chains {

    my $res = {};

    # check what chains we want to track
    my $is_pvefw_chain = sub {
	my $name = shift;

	return 1 if $name =~ m/^PVEFW-\S+$/;

	return 1 if $name =~ m/^tap\d+i\d+-(:?IN|OUT)$/;
	return 1 if $name =~ m/^vmbr\d+-(:?IN|OUT)$/;
	return 1 if $name =~ m/^GROUP-(:?[^\s\-]+)-(:?IN|OUT)$/;

	return undef;
    };

    my $table = '';

    my $parser = sub {
	my $line = shift;

	return if $line =~ m/^#/;
	return if $line =~ m/^\s*$/;

	if ($line =~ m/^\*(\S+)$/) {
	    $table = $1;
	    return;
	}

	return if $table ne 'filter';

	if ($line =~ m/^:(\S+)\s/) {
	    my $chain = $1;
	    return if !&$is_pvefw_chain($chain);
	    $res->{$chain} = "unknown";
	} elsif ($line =~ m/^-A\s+(\S+)\s.*--comment\s+\"PVESIG:(\S+)\"/) {
	    my ($chain, $sig) = ($1, $2);
	    return if !&$is_pvefw_chain($chain);
	    $res->{$chain} = $sig;
	} else {
	    # simply ignore the rest
	    return;
	}
    };

    run_command("/sbin/iptables-save", outfunc => $parser);

    return $res;
}

sub iptables_chain_exist {
    my ($chain) = @_;

    eval{
	iptables("-n --list $chain");
    };
    return undef if $@;

    return 1;
}

sub iptables_rule_exist {
    my ($rule) = @_;

    eval{
	iptables("-C $rule");
    };
    return undef if $@;

    return 1;
}

sub ruleset_generate_rule {
    my ($ruleset, $chain, $rule, $goto) = @_;

    my $cmd = '';

    $cmd .= " -m iprange --src-range" if $rule->{nbsource} && $rule->{nbsource} > 1;
    $cmd .= " -s $rule->{source}" if $rule->{source};
    $cmd .= " -m iprange --dst-range" if $rule->{nbdest} && $rule->{nbdest} > 1;
    $cmd .= " -d $rule->{dest}" if $rule->{destination};
    $cmd .= " -p $rule->{proto}" if $rule->{proto};
    $cmd .= "  --match multiport" if $rule->{nbdport} && $rule->{nbdport} > 1;
    $cmd .= " --dport $rule->{dport}" if $rule->{dport};
    $cmd .= "  --match multiport" if $rule->{nbsport} && $rule->{nbsport} > 1;
    $cmd .= " --sport $rule->{sport}" if $rule->{sport};

    if (my $action = $rule->{action}) {
	$goto = 1 if !defined($goto) && $action eq 'PVEFW-SET-ACCEPT-MARK';
	$cmd .= $goto ? " -g $action" : " -j $action";
    };

    ruleset_addrule($ruleset, $chain, $cmd) if $cmd;
}

sub ruleset_create_chain {
    my ($ruleset, $chain) = @_;

    die "Invalid chain name '$chain' (28 char max)\n" if length($chain) > 28;

    die "chain '$chain' already exists\n" if $ruleset->{$chain};

    $ruleset->{$chain} = [];
}

sub ruleset_chain_exist {
    my ($ruleset, $chain) = @_;

    return $ruleset->{$chain} ? 1 : undef;
}

sub ruleset_addrule {
   my ($ruleset, $chain, $rule) = @_;

   die "no such chain '$chain'\n" if !$ruleset->{$chain};

   push @{$ruleset->{$chain}}, "-A $chain $rule";
}

sub ruleset_insertrule {
   my ($ruleset, $chain, $rule) = @_;

   die "no such chain '$chain'\n" if !$ruleset->{$chain};

   unshift @{$ruleset->{$chain}}, "-A $chain $rule";
}

sub generate_bridge_chains {
    my ($ruleset, $bridge) = @_;

    if (!ruleset_chain_exist($ruleset, "PVEFW-BRIDGE-IN")){
	ruleset_create_chain($ruleset, "PVEFW-BRIDGE-IN");
    }

    if (!ruleset_chain_exist($ruleset, "PVEFW-BRIDGE-OUT")){
	ruleset_create_chain($ruleset, "PVEFW-BRIDGE-OUT");
    }

    if (!ruleset_chain_exist($ruleset, "PVEFW-FORWARD")){
	ruleset_create_chain($ruleset, "PVEFW-FORWARD");

	ruleset_addrule($ruleset, "PVEFW-FORWARD", "-m state --state RELATED,ESTABLISHED -j ACCEPT");
	ruleset_addrule($ruleset, "PVEFW-FORWARD", "-m physdev --physdev-is-in --physdev-is-bridged -j PVEFW-BRIDGE-OUT");
	ruleset_addrule($ruleset, "PVEFW-FORWARD", "-m physdev --physdev-is-out --physdev-is-bridged -j PVEFW-BRIDGE-IN");
    }

    if (!ruleset_chain_exist($ruleset, "$bridge-IN")) {
	ruleset_create_chain($ruleset, "$bridge-IN");
	ruleset_addrule($ruleset, "PVEFW-FORWARD", "-i $bridge -j DROP");  # disable interbridge routing
	ruleset_addrule($ruleset, "PVEFW-BRIDGE-IN", "-j $bridge-IN");
	ruleset_addrule($ruleset, "$bridge-IN", "-j ACCEPT");
    }

    if (!ruleset_chain_exist($ruleset, "$bridge-OUT")) {
	ruleset_create_chain($ruleset, "$bridge-OUT");
	ruleset_addrule($ruleset, "PVEFW-FORWARD", "-o $bridge -j DROP"); # disable interbridge routing
	ruleset_addrule($ruleset, "PVEFW-BRIDGE-OUT", "-j $bridge-OUT");
    }
}

sub generate_tap_rules_direction {
    my ($ruleset, $iface, $netid, $macaddr, $rules, $bridge, $direction) = @_;

    my $tapchain = "$iface-$direction";

    ruleset_create_chain($ruleset, $tapchain);

    ruleset_addrule($ruleset, $tapchain, "-m state --state INVALID -j DROP");
    ruleset_addrule($ruleset, $tapchain, "-m state --state RELATED,ESTABLISHED -j ACCEPT");

    if ($direction eq 'OUT' && defined($macaddr)) {
	ruleset_addrule($ruleset, $tapchain, "-m mac ! --mac-source $macaddr -j DROP");
    }

    if ($rules) {
        foreach my $rule (@$rules) {
	    next if $rule->{iface} && $rule->{iface} ne $netid;
	    if($rule->{action}  =~ m/^(GROUP-(\S+))$/){
		$rule->{action} .= "-$direction";
		# generate empty group rule if don't exist
		if(!ruleset_chain_exist($ruleset, $rule->{action})){
		    generate_group_rules($ruleset, $2);
		}
		ruleset_generate_rule($ruleset, $tapchain, $rule);
		ruleset_addrule($ruleset, $tapchain, "-m mark --mark 1 -g $bridge-IN");
	    } else {
		# we go to vmbr-IN if accept in out rules
		$rule->{action} = "$bridge-IN" if $rule->{action} eq 'ACCEPT' && $direction eq 'OUT';
		ruleset_generate_rule($ruleset, $tapchain, $rule);
	    }
	}
    }

    ruleset_addrule($ruleset, $tapchain, "-j LOG --log-prefix \"$tapchain-dropped: \" --log-level 4");
    ruleset_addrule($ruleset, $tapchain, "-j DROP");

    # plug the tap chain to bridge chain
    my $physdevdirection = $direction eq 'IN' ? "out" : "in";
    my $rule = "-m physdev --physdev-$physdevdirection $iface --physdev-is-bridged -j $tapchain";
    ruleset_insertrule($ruleset, "$bridge-$direction", $rule);

    if ($direction eq 'OUT'){
	# add tap->host rules
	my $rule = "-m physdev --physdev-$physdevdirection $iface -j $tapchain";
	ruleset_addrule($ruleset, "PVEFW-INPUT", $rule);
    }
}

sub enablehostfw {
    my ($ruleset) = @_;

    my $filename = "/etc/pve/local/host.fw";
    my $fh = IO::File->new($filename, O_RDONLY);
    return if !$fh;

    my $rules = parse_fw_rules($filename, $fh);

    # host inbound firewall
    my $chain = "PVEFW-HOST-IN";
    ruleset_create_chain($ruleset, $chain);

    ruleset_addrule($ruleset, $chain, "-m state --state INVALID -j DROP");
    ruleset_addrule($ruleset, $chain, "-m state --state RELATED,ESTABLISHED -j ACCEPT");
    ruleset_addrule($ruleset, $chain, "-i lo -j ACCEPT");
    ruleset_addrule($ruleset, $chain, "-m addrtype --dst-type MULTICAST -j ACCEPT");
    ruleset_addrule($ruleset, $chain, "-p udp -m state --state NEW -m multiport --dports 5404,5405 -j ACCEPT");
    ruleset_addrule($ruleset, $chain, "-p udp -m udp --dport 9000 -j ACCEPT");  #corosync

    if ($rules->{in}) {
        foreach my $rule (@{$rules->{in}}) {
            # we use RETURN because we need to check also tap rules
            $rule->{action} = 'RETURN' if $rule->{action} eq 'ACCEPT';
            ruleset_generate_rule($ruleset, $chain, $rule);
        }
    }

    ruleset_addrule($ruleset, $chain, "-j LOG --log-prefix \"kvmhost-IN dropped: \" --log-level 4");
    ruleset_addrule($ruleset, $chain, "-j DROP");

    # host outbound firewall
    $chain = "PVEFW-HOST-OUT";
    ruleset_create_chain($ruleset, $chain);

    ruleset_addrule($ruleset, $chain, "-m state --state INVALID -j DROP");
    ruleset_addrule($ruleset, $chain, "-m state --state RELATED,ESTABLISHED -j ACCEPT");
    ruleset_addrule($ruleset, $chain, "-o lo -j ACCEPT");
    ruleset_addrule($ruleset, $chain, "-m addrtype --dst-type MULTICAST -j ACCEPT");
    ruleset_addrule($ruleset, $chain, "-p udp -m state --state NEW -m multiport --dports 5404,5405 -j ACCEPT");
    ruleset_addrule($ruleset, $chain, "-p udp -m udp --dport 9000 -j ACCEPT"); #corosync

    if ($rules->{out}) {
        foreach my $rule (@{$rules->{out}}) {
            # we use RETURN because we need to check also tap rules
            $rule->{action} = 'RETURN' if $rule->{action} eq 'ACCEPT';
            ruleset_generate_rule($ruleset, $chain, $rule);
        }
    }

    ruleset_addrule($ruleset, $chain, "-j LOG --log-prefix \"kvmhost-OUT dropped: \" --log-level 4");
    ruleset_addrule($ruleset, $chain, "-j DROP");
    
    ruleset_addrule($ruleset, "PVEFW-OUTPUT", "-j PVEFW-HOST-OUT");
    ruleset_addrule($ruleset, "PVEFW-INPUT", "-j PVEFW-HOST-IN");
}

sub generate_group_rules {
    my ($ruleset, $group) = @_;

    my $filename = "/etc/pve/firewall/groups.fw";
    my $fh = IO::File->new($filename, O_RDONLY);
    return if !$fh;

    my $rules = parse_fw_rules($filename, $fh, $group);

    my $chain = "GROUP-${group}-IN";

    ruleset_create_chain($ruleset, $chain);

    if ($rules->{in}) {
        foreach my $rule (@{$rules->{in}}) {
 	    ruleset_generate_rule($ruleset, $chain, $rule);
        }
    }

    $chain = "GROUP-${group}-OUT";

    ruleset_create_chain($ruleset, $chain);
    ruleset_addrule($ruleset, $chain, "-j MARK --set-mark 0"); # clear mark

    if ($rules->{out}) {
        foreach my $rule (@{$rules->{out}}) {
            # we go the PVEFW-SET-ACCEPT-MARK Instead of ACCEPT) because we need to 
	    # check also other tap rules (and group rules can be set on any bridge, 
	    # so we can't go to VMBRXX-IN)
            $rule->{action} = 'PVEFW-SET-ACCEPT-MARK' if $rule->{action} eq 'ACCEPT';
            ruleset_generate_rule($ruleset, $chain, $rule);
        }
    }
}

sub parse_fw_rules {
    my ($filename, $fh, $group) = @_;

    my $section;
    my $securitygroup;
    my $securitygroupexist;

    my $res = { in => [], out => [] };

    my $macros = get_firewall_macros();
    my $protocols = get_etc_protocols();
    
    while (defined(my $line = <$fh>)) {
	next if $line =~ m/^#/;
	next if $line =~ m/^\s*$/;

	if ($line =~ m/^\[(in|out)(:(\S+))?\]\s*$/i) {
	    $section = lc($1);
	    $securitygroup = lc($3) if $3;
	    $securitygroupexist = 1 if $securitygroup &&  $securitygroup eq $group;
	    next;
	}
	next if !$section;
	next if $group && $securitygroup ne $group;

	my ($action, $iface, $source, $dest, $proto, $dport, $sport) =
	    split(/\s+/, $line);

	if (!$action) {
	    warn "skip incomplete line\n";
	    next;
	}

	my $service;
	if ($action =~ m/^(ACCEPT|DROP|REJECT|GROUP-(\S+))$/) {
	    # OK
	} elsif ($action =~ m/^(\S+)\((ACCEPT|DROP|REJECT)\)$/) {
	    ($service, $action) = ($1, $2);
	    if (!$macros->{$service}) {
		warn "unknown service '$service'\n";
		next;
	    }
	} else {
	    warn "unknown action '$action'\n";
	    next;
	}

	$iface = undef if $iface && $iface eq '-';
	if ($iface && $iface !~ m/^(net0|net1|net2|net3|net4|net5)$/) {
	    warn "unknown interface '$iface'\n";
	    next;
	}

	$proto = undef if $proto && $proto eq '-';
	if ($proto && !(defined($protocols->{byname}->{$proto}) ||
			defined($protocols->{byid}->{$proto}))) {
	    warn "unknown protokol '$proto'\n";
	    next;
	}

	$source = undef if $source && $source eq '-';
	$dest = undef if $dest && $dest eq '-';

	$dport = undef if $dport && $dport eq '-';
	$sport = undef if $sport && $sport eq '-';
	my $nbdport = undef;
	my $nbsport = undef;
	my $nbsource = undef;
	my $nbdest = undef;

	eval {
	    $nbsource = parse_address_list($source) if $source;
	    $nbdest = parse_address_list($dest) if $dest;
	    $nbdport = parse_port_name_number_or_range($dport) if $dport;
	    $nbsport = parse_port_name_number_or_range($sport) if $sport;
	};
	if (my $err = $@) {
	    warn $err;
	    next;

	}


	my $rule = {
	    action => $action,
	    service => $service,
	    iface => $iface,
	    source => $source,
	    dest => $dest,
	    nbsource => $nbsource,
	    nbdest => $nbdest,
	    proto => $proto,
	    dport => $dport,
	    sport => $sport,
	    nbdport => $nbdport,
	    nbsport => $nbsport,

	};

	push @{$res->{$section}}, $rule;
    }

    die "security group $group don't exist" if $group && !$securitygroupexist;
    return $res;
}

sub run_locked {
    my ($code, @param) = @_;

    my $timeout = 10;

    my $res = lock_file($pve_fw_lock_filename, $timeout, $code, @param);

    die $@ if $@;

    return $res;
}

sub read_local_vm_config {

    my $openvz = {};

    my $qemu = {};

    my $list = PVE::QemuServer::config_list();

    foreach my $vmid (keys %$list) {
	my $cfspath = PVE::QemuServer::cfs_config_path($vmid);
	if (my $conf = PVE::Cluster::cfs_read_file($cfspath)) {
	    $qemu->{$vmid} = $conf;
	}
    }

    my $vmdata = { openvz => $openvz, qemu => $qemu };

    return $vmdata;
};

sub read_vm_firewall_rules {
    my ($vmdata) = @_;
    my $rules = {};
    foreach my $vmid (keys %{$vmdata->{qemu}}, keys %{$vmdata->{openvz}}) {
	my $filename = "/etc/pve/firewall/$vmid.fw";
	my $fh = IO::File->new($filename, O_RDONLY);
	next if !$fh;

	$rules->{$vmid} = parse_fw_rules($filename, $fh);
    }

    return $rules;
}

sub compile {
    my $vmdata = read_local_vm_config();
    my $rules = read_vm_firewall_rules($vmdata);

    #print Dumper($rules);

    my $ruleset = {};

    # setup host firewall rules
    ruleset_create_chain($ruleset, "PVEFW-INPUT");
    ruleset_create_chain($ruleset, "PVEFW-OUTPUT");

    ruleset_create_chain($ruleset, "PVEFW-SET-ACCEPT-MARK");
    ruleset_addrule($ruleset, "PVEFW-SET-ACCEPT-MARK", "-j MARK --set-mark 1");

    enablehostfw($ruleset);

    # generate firewall rules for QEMU VMs 
    foreach my $vmid (keys %{$vmdata->{qemu}}) {
	my $conf = $vmdata->{qemu}->{$vmid};
	next if !$rules->{$vmid};

	foreach my $netid (keys %$conf) {
	    next if $netid !~ m/^net(\d+)$/;
	    my $net = PVE::QemuServer::parse_net($conf->{$netid});
	    next if !$net;
	    my $iface = "tap${vmid}i$1";

	    my $bridge = $net->{bridge};
	    next if !$bridge; # fixme: ?

	    $bridge .= "v$net->{tag}" if $net->{tag};

	    generate_bridge_chains($ruleset, $bridge);

	    my $macaddr = $net->{macaddr};
	    generate_tap_rules_direction($ruleset, $iface, $netid, $macaddr, $rules->{$vmid}->{in}, $bridge, 'IN');
	    generate_tap_rules_direction($ruleset, $iface, $netid, $macaddr, $rules->{$vmid}->{out}, $bridge, 'OUT');
	}
    }
    return $ruleset;
}

sub get_ruleset_status {
    my ($ruleset, $verbose) = @_;

    my $active_chains = iptables_get_chains();

    my $statushash = {};

    foreach my $chain (sort keys %$ruleset) {
	my $digest = Digest::SHA->new('sha1');
	foreach my $cmd (@{$ruleset->{$chain}}) {
	     $digest->add("$cmd\n");
	}
	my $sig = $digest->b64digest;
	$statushash->{$chain}->{sig} = $sig;

	my $oldsig = $active_chains->{$chain};
	if (!defined($oldsig)) {
	    $statushash->{$chain}->{action} = 'create';
	} else {
	    if ($oldsig eq $sig) {
		$statushash->{$chain}->{action} = 'exists';
	    } else {
		$statushash->{$chain}->{action} = 'update';
	    }
	}
	print "$statushash->{$chain}->{action} $chain ($sig)\n" if $verbose;
	foreach my $cmd (@{$ruleset->{$chain}}) {
	    print "\t$cmd\n" if $verbose;
	}
    }

    foreach my $chain (sort keys %$active_chains) {
	if (!defined($ruleset->{$chain})) {
	    my $sig = $active_chains->{$chain};
	    $statushash->{$chain}->{action} = 'delete';
	    $statushash->{$chain}->{sig} = $sig;
	    print "delete $chain ($sig)\n" if $verbose;
	}
    }    

    return $statushash;
}

sub print_ruleset {
    my ($ruleset) = @_;

    get_ruleset_status($ruleset, 1);
}

sub print_sig_rule {
    my ($chain, $sig) = @_;

    # We just use this to store a SHA1 checksum used to detect changes
    return "-A $chain -m comment --comment \"PVESIG:$sig\"\n";
}

sub apply_ruleset {
    my ($ruleset, $verbose) = @_;

    enable_bridge_firewall();

    my $cmdlist = "*filter\n"; # we pass this to iptables-restore;

    my $statushash = get_ruleset_status($ruleset, $verbose);

    # create missing chains first
    foreach my $chain (sort keys %$ruleset) {
	my $stat = $statushash->{$chain};
	die "internal error" if !$stat;
	next if $stat->{action} ne 'create';

	$cmdlist .= ":$chain - [0:0]\n";
    }

    my $rule = "INPUT -j PVEFW-INPUT";
    if (!PVE::Firewall::iptables_rule_exist($rule)) {
	$cmdlist .= "-A $rule\n";
    }
    $rule = "OUTPUT -j PVEFW-OUTPUT";
    if (!PVE::Firewall::iptables_rule_exist($rule)) {
	$cmdlist .= "-A $rule\n";
    }

    $rule = "FORWARD -j PVEFW-FORWARD";
    if (!PVE::Firewall::iptables_rule_exist($rule)) {
	$cmdlist .= "-A $rule\n";
    }

    foreach my $chain (sort keys %$ruleset) {
	my $stat = $statushash->{$chain};
	die "internal error" if !$stat;

	if ($stat->{action} eq 'update' || $stat->{action} eq 'create') {
	    $cmdlist .= "-F $chain\n";
	    foreach my $cmd (@{$ruleset->{$chain}}) {
		$cmdlist .= "$cmd\n";
	    }
	    $cmdlist .= print_sig_rule($chain, $stat->{sig});
	} elsif ($stat->{action} eq 'delete') {
	    die "internal error"; # this should not happen
	} elsif ($stat->{action} eq 'exists') {
	    # do nothing
	} else {
	    die "internal error - unknown status '$stat->{action}'";
	}
    }

    foreach my $chain (keys %$statushash) {
	next if $statushash->{$chain}->{action} ne 'delete';
	$cmdlist .= "-F $chain\n";
    }
    foreach my $chain (keys %$statushash) {
	next if $statushash->{$chain}->{action} ne 'delete';
	$cmdlist .= "-X $chain\n";
    }

    $cmdlist .= "COMMIT\n";

    print $cmdlist if $verbose;

    iptables_restore_cmdlist($cmdlist);

    # test: re-read status and check if everything is up to date 
    $statushash = get_ruleset_status($ruleset);

    my $errors;
    foreach my $chain (sort keys %$ruleset) {
	my $stat = $statushash->{$chain};
	if ($stat->{action} ne 'exists') {
	    warn "unable to update chain '$chain'\n";
	    $errors = 1;
	}
    }

    die "unable to apply firewall changes\n" if $errors;
}

1;