NHIPT - iptables firewall GUI¶
iptables is a command-line interface for configuring the high - sophisticated netfilter Linux kernel firewall. The nhipt web front-end exposes the whole potential of iptables in a user-friendly UI of your FritzBox and leverages this consumer device to the level of a professional firewall, supporting both IPv4 & IPv6 Layer-3 protocols. The UI can be either integrated in your firmware image or run stand-alone externally from an attached device (e.g. USB-Stick).
- iptables have to be installed and running. It is recommended to build at least the following kernel modules in your firmware image (the more you choose, the more fun you’ll have):
* ip_tables * x_tables * iptable_filter * ip_conntrack * ip_conntrack_ftp * ip_conntrack_tftp * ipt_log * ipt_REJECT * ipt_iprange * xt_state * xt_conntrack * xt_multiport * xt_tcpudp
!!! Please don’t forget to include the according shared libraries too in your firmware image !!!
The ideal build includes a replaced kernel with autoload kernel modules enabled (make kernel-menuconfig → Loadable modules support → Automatic kernel module loading).Prior to first use you must start iptables either by : iptables -S (if you have a replaced kernel with automatic kernel modules loading)or (whithout autoload) by using modprobe <modulname> for each module.
YOU HAVE THE CHOICE OF 3 INSTALL OPTIONS:¶
This is the naked GUI - you can run it directly from an USB stick, without the integration in freetz.
- copy the file nhipt.cgi to your stick (e.g. to: /var/media/ftp/uStor01/ipt/cgi-bin)
- set execute permissions to the file.
- set up the httpd deamon for the UI on the folder above of the cgi-bin (e.g. to/ipt) and use a free tcp port (e.g. 83).
chmod +x /var/media/ftp/uStor01/ipt/cgi-bin/nhipt.cgi httpd -P /var/run/nhipt.pid -p 83 -h /var/media/ftp/uStor01/ipt
Now you can access the UI via http://fritz.box:83/cgi-bin/nhipt.cgi
The external comfort package with freetz integration
- unpack to /var/media/ftp/uStor01/.
- set execute permissions to register.sh
- run register.sh
chmod +x /var/media/ftp/uStor01/ipt/register.sh . /var/media/ftp/uStor01/ipt/register.sh
Now you should have a brand-new package in the freetz UI, where you can configure all the installation options.
BEHIND THE SCENES:¶
The interface reads interactively the current rule set of your firewall and enables you to edit all rules, tables, chains, policies etc. online and life! This means, after submitting your changes the new rule immediately takes effect. The bad news are: You can accidentally lock out yourself - the good news are: it does not matter - the rule is not persistently saved - just reboot your box to the last known good rule set. When you have finished playing around with your rules and everything works as you like it you can click on [Persist rules] to save your work permanently and reboot-resistant either to the flash memory of the box or to the attached USB device [BOOT FROM FLASH / USB] + [SET BOOT DIRECTORY]. You can either use the guided UI to alter / add your rules for each chain or you can enter your rules using the command line expert interface on top. To add additional tables and modules use the selection checkboxes or modprobe them by hand in the expert UI. If you have ipv6 enabled and loaded, the UI also shows you the filter tables for ipv6.
For security reason you can limit the access to the UI to a dedicated Admin-IP or Admin-IP-Range using: [SET / CHANGE ADMIN IP].
For the DECT boxes there is an option to set up an internal log deamon to catch the deviated kernel messages and present them in the UI. The log directory can be set up to any writeable destination.
Error and system messages are shown in the bottom lines of the UI for your information, status 0 means OK.
- debug.cfg can be used to bootstrap the iptables rulset.
- rc.nhipt load is called by rc.mod / run level 20 and checks, if debug.cfg has startet the firewall, otherwise /tmp/flash/nhiptboot.cfg is called to initialize the firewall
- debug.cfg and nhiptboot.cfg use the same script settings and
- wait - if configured for USB ready or time-out
- copy the settings file nhipt.par as configured from the source (flash / USB) to the RAM disc
- copy the start script nhipt.cfg to the RAM disc
- run the start script nhipt.cfg detached in the background.
- stop dsld if configured for security reason
- wait for delay timer (if configured to prevent mistakenly lock-out)
- start dsld if configured
- start Web-Server for the UI
- start internal log-deamon if configured
- load all saved rules
Scenario 1: stand-alone CGI - boots always from debug.cfg, rules can be saved either to the flash or to the usb stick.
Scenario 2: dynamic freetz - boots either from debug.cfg or delayed from freetz rc.custom (rc.custom is used to re-integrate the dynamic modules in freetz after reboot)
Scenario 3: Runlevel of Freetz - integrated start-up, optional debug.cfg can be used for early protection.
BACK=/var/media/ftp/uStor01/save CHANGED=0 DELAY=0 LOGTARGET=internal DSLDOFF=0 ADMINIP= LOGD=/var/media/ftp/uStor01/log AIRBAG=0 MYIP= BOOTSTRAP=freetz PORT=83 BOOT=flash BOOTDIR=/tmp/flash ROOT=/usr/ipt
files contained in the freetz package¶
/etc/default.nhipt/nhipt.cfg rwxrwxrwx # config for freetz UI /etc/init.d/rc.nhipt r-xr-xr-x # call-back for freetz UI, boot loader /usr/ipt/index.html r--r--r-- # frameset for UI /usr/ipt/cgi-bin/nhipt.cgi r-xr-xr-x # the CGI for iptables /lib/cgi-bin/nhipt.cgi r-xr-xr-x # the CGI for freetz settings
Unexperianced users should read this carefully to prevent permanent lock-outs.
Firewalls protect systems from intruders based on rules and policies. They are obeyed by the system - the system cannot guess who is good and who’s bad. Eventually even experienced firewall admin’s can lock themselves out. It is good to know, how to recover from this in advance.
The following hints can make your life easier:
- you can look at all scripts - but don’t change them manually, if you are not certain what they do exactly.
- save rule sets permanently only if everything works as it should - test at least your admin access to the box. Use the BackUp Option so you can start over from a known-good set-up.
- Use in the beginning the usb stick as boot target. If you lock-out yourself - just pull out the stick and reboot. No iptables will be loaded!
- For Newbees there is a [safe] Mode. The firewall automatically takes care, that under all circumstances the Admin-IP will not be locked-out from the box (IPv4 only).
- switching back to [advanced] lets you remove this safety rules later.
- use the [Boot-Delay] option - this gives you some time to login and kill your naughty rule-set.
- if you enter a wrong Admin-IP and lock yourself out from the UI - no problem. Use freetz UI to fix or edit /var/tmp/nhipt.par - Delete the ADMINIP= Entry.
- if you ignore all this hints and finally lock yourself - the last chance is to flash a brand new image without iptables and delete the rules manually.