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rebuild-iptables
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rebuild-iptables
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#!/usr/bin/perl -w
our $ID = q$Id: rebuild-iptables 344 2006-10-04 02:48:30Z digant $;
#
# rebuild-iptables -- Construct an iptables rules file from fragments.
#
# Written by Russ Allbery <rra@stanford.edu>
# Adapted by Digant C Kasundra <digant@stanford.edu>
# Adapted by Joe Williams (2011) <joe@joetify.com>
# Copyright 2005, 2006 Board of Trustees, Leland Stanford Jr. University
#
# Constructs an iptables rules file from the prefix, standard, and suffix
# files in the iptables configuration area, adding any additional modules
# specified in the command line, and prints the resulting iptables rules to
# standard output (suitable for saving into /var/lib/iptables or some other
# appropriate location on the system).
##############################################################################
# Modules and declarations
##############################################################################
require 5.006;
use strict;
use Getopt::Long qw(GetOptions);
# Path to the iptables template area.
our $TEMPLATE = '/etc/iptables.d';
##############################################################################
# Installation
##############################################################################
# Return the prefix
sub prefix {
my $data;
( $data = <<'END_OF_PREFIX' ) =~ s/^\s+//gm;
*filter
:INPUT ACCEPT
:FORWARD ACCEPT
:OUTPUT ACCEPT
:FWR -
-A INPUT -j FWR
-A FWR -i lo -j ACCEPT
END_OF_PREFIX
return $data;
}
# Return the suffix
sub suffix {
my $data;
( $data = <<'END_OF_SUFFIX' ) =~ s/^\s+//gm;
# Rejects all remaining connections with port-unreachable errors.
-A FWR -p tcp -m tcp --tcp-flags SYN,RST,ACK SYN -j REJECT --reject-with icmp-port-unreachable
-A FWR -p udp -j REJECT --reject-with icmp-port-unreachable
COMMIT
END_OF_SUFFIX
return $data;
}
sub snat {
my $data = "";
if ( -f "/etc/iptables.snat" ) {
open( SNAT, "<", "/etc/iptables.snat" )
or die "$0: cannot open /etc/iptables.snat: $!\n";
while (<SNAT>) {
$data = $data . $_;
}
close(SNAT);
}
return $data;
}
# Read in a file, processing includes as required. Returns the contents of
# the file as an array.
sub read_iptables {
my ($file) = @_;
my @data;
$file = $TEMPLATE . '/' . $file unless $file =~ m%^\.?/%;
local *MODULE;
open( MODULE, '<', $file ) or die "$0: cannot open $file: $!\n";
local $_;
while (<MODULE>) {
if (/^\s*include\s+(\S+)$/) {
my $included = $1;
$included = $TEMPLATE . '/' . $included
unless $included =~ m%^\.?/%;
if ( $file eq $included ) {
die "$0: include loop in $file, line $.\n";
}
push( @data, "\n" );
push( @data, read_iptables($included) );
push( @data, "\n" );
} elsif (/^\s*include\s/) {
die "$0: malformed include line in $file, line $.\n";
} else {
push( @data, $_ );
}
}
close MODULE;
return @data;
}
# Write a file carefully.
sub write_iptables {
my ( $file, @data ) = @_;
open( NEW, "> $file.new" ) or die "$0: cannot create $file.new: $!\n";
print NEW @data or die "$0: cannot write to $file.new: $!\n";
close NEW or die "$0: cannot flush $file.new: $!\n";
rename( "$file.new", $file )
or die "$0: cannot install new $file: $!\n";
}
# Install iptables on a Red Hat system. Takes the array containing the new
# iptables data.
sub install_redhat {
my (@data) = @_;
write_iptables( '/etc/sysconfig/iptables', @data );
system( "/sbin/service", "iptables", "restart" );
}
# Install iptables on a Debian system. Take the array containing the new
# iptables data.
sub install_debian {
my (@data) = @_;
unless ( -d '/etc/iptables' ) {
mkdir( '/etc/iptables', 0755 )
or die "$0: cannot mkdir /etc/iptables: $!\n";
}
write_iptables( "/etc/iptables/general", @data );
system("/sbin/iptables-restore < /etc/iptables/general") == 0
or die "rebuild-iptables: iptables-restore failed! - $?"
}
##############################################################################
# Main routine
##############################################################################
# Fix things up for error reporting.
$| = 1;
my $fullpath = $0;
$0 =~ s%.*/%%;
# Parse command-line options.
my ( $help, $version );
Getopt::Long::config( 'bundling', 'no_ignore_case' );
GetOptions(
'h|help' => \$help,
'v|version' => \$version
) or exit 1;
if ($help) {
print "Feeding myself to perldoc, please wait....\n";
exec( 'perldoc', '-t', $fullpath );
} elsif ($version) {
my $version = join( ' ', ( split( ' ', $ID ) )[ 1 .. 3 ] );
$version =~ s/,v\b//;
$version =~ s/(\S+)$/($1)/;
$version =~ tr%/%-%;
print $version, "\n";
exit;
}
my @modules;
if ( -d '/etc/iptables.d' ) {
@modules = </etc/iptables.d/*>;
}
# Concatenate everything together.
my @data;
push( @data, prefix() );
push( @data, "\n" );
for my $module (@modules) {
push( @data, read_iptables($module) );
push( @data, "\n" );
}
push( @data, suffix() );
push( @data, snat() );
if ( -f '/etc/debian_version' ) {
install_debian(@data);
} elsif ( -f '/etc/redhat-release' ) {
install_redhat(@data);
} else {
die "$0: cannot figure out whether this is Red Hat or Debian\n";
}
exit 0;
__END__
##############################################################################
# Documentation
##############################################################################
=head1 NAME
rebuild-iptables - Construct an iptables rules file from fragments
=head1 SYNOPSIS
rebuild-iptables [B<-hv>]
=head1 DESCRIPTION
B<rebuild-iptables> constructs an iptables configuration file by concatenating
various modules found in F</etc/iptables.d>. The resulting iptables
configuration file is written to the appropriate file for either Red Hat or
Debian (determined automatically) and iptables is restarted.
Each module is just a text file located in the directory mentioned above that
contains one or more iptables configuration lines (basically the arguments to
an B<iptables> invocation), possibly including comments.
Along with the modules in the directory specified, a standard prefix and suffix
is added.
Normally, the contents of each module are read in verbatim, but a module may
also contain the directive:
include <module>
on a separate line, where <module> is the path to another module to include,
specified the same way as modules given on the command line (hence, either a
file name relative to F</afs/ir/service/jumpstart/data/iptables> or an
absolute path). Such a line will be replaced with the contents of the named
file. Be careful when using this directive to not create loops; files
including themselves will be detected, but more complex loops will not and
will result in infinite output.
=head1 OPTIONS
=over 4
=item B<-h>, B<--help>
Print out this documentation (which is done simply by feeding the script to
C<perldoc -t>).
=item B<-v>, B<--version>
Print out the version of B<rebuild-iptables> and exit.
=back
=head1 FILES
=over 4
=item F</etc/iptables.d>
The default module location.
=item F</etc/debian_version>
If this file exists, the system is assumed to be a Debian system for
determining the installation location when B<-i> is used.
=item F</etc/iptables/general>
The install location of the generated configuration file on Debian.
=item F</etc/redhat-release>
If this file exists, the system is assumed to be a Red Hat system for
determining the installation location when B<-i> is used.
=item F</etc/sysconfig/iptables>
The install location of the generated configuration file on Red Hat.
=back
=head1 AUTHOR
Russ Allbery <rra@stanford.edu>
Digant C Kasundra <digant@stanford.edu>
=head1 SEE ALSO
iptables(8)
=cut