ipfw divert filter for IPv4 geo-blocking

[Dr. Rolf Jansen]

> Am 26.07.2016 um 23:03 schrieb Julian Elischer <julian at freebsd.org>:
> On 27/07/2016 3:06 AM, Dr. Rolf Jansen wrote:
>> There is another tool called geoip , that I uploaded to GitHub, and that I use for looking up country codes by IP addresses on the command line.
>> 
>>     https://github.com/cyclaero/ipdb/blob/master/geoip.c
>> 
>> This one could easily be extended to produce sorted IP ranges per CC that could be fed into tables of ipfw. I am thinking of adding a command line option for specifying CC's for which the IP ranges should be exported, something like:
>> 
>>    geoip -e DE:BR:US:IT:FR:ES
>> 
>> And this could print sorted IP-Ranges belonging to the listed countries. For this purpose, what would be the ideal format for directly feeding the produced output into ipfw tables?
> The format for using tables directly is the same as that used for routing tables.
> …
> table 5 add 1.1.1.0/32 1000
> …
> your application becomes an application for configuring the firewall.
> (which you do by feeding commands down a pipe to ipfw, which is started as 'ipfw -q /dev/stdin')

I finished adding a second usage form for the geoip tool, namely generation of ipfw table construction directives filtered by country codes.

______________
$ geoip -h
geoip v1.0.1 (16), Copyright © 2016 Dr. Rolf Jansen

Usage:

1) look-up the country code belonging to an IPv4 address given by the last command line argument:

   geoip [-r bstfile] [-h] <dotted IPv4 address>
      <IPv4 address>    a dotted IPv4 address to be looked-up.

2) generate a sorted list of IPv4 address/masklen pairs per country code, formatted as ipfw table construction directives:

   geoip -t [CC:DD:EE:..] [-n table number] [-v table value] [-r bstfile] [-h]

      -t [CC:DD:EE:..]  output all IPv4 address/masklen pairs belonging to the listed countries, given by 2 letter
                        capital country codes, separated by colon. An empty CC list means any country code.
      -n table number   the ipfw table number between 0 and 65534 [default: 0].
      -v table value    the 32-bit unsigned value of the ipfw table entry [default: 0].

valid arguments in both usage forms:

      -r bstfile        the path to the binary file with the consolidated IP ranges that has been.
                        generated by the 'ipdb' tool [default: /usr/local/etc/ipdb/IPRanges/ipcc.bst].
      -h                show these usage instructions.
______________

With that, the ipfw configuration script may contain something alike:

    …
    # allow only web access from DE, BR, US:
    /usr/local/bin/geoip -t DE:BR:US -n 7 | /sbin/ipfw -q /dev/stdin
    /sbin/ipfw -q add 70 deny tcp from not table\(7\) to any 80,443 in recv WAN_if setup
    …

OR, the other way around:
    …
    # deny web access from certain disgraceful regions:
    /usr/local/bin/geoip -t KO:TR:SA:RU:GB -n 66 | /sbin/ipfw -q /dev/stdin
    /sbin/ipfw -q add 70 allow tcp from not table\(66\) to any 80,443 in recv WAN_if setup
    …
____________


Best regards

Rolf