ipset is command line utility that allows the firewall admins to manage large lists of IPs.
ipset is independent of
iptables. Once a collection of IPs has been created with
iptables and FireHOL can use it. Adding or removing IPs to/from the collection, does not need any change at the firewall. Collections are manipulated by the ipset command and the firewall will automatically use the new IPs.
ipset collection is defined by its name. To create an new collection run on a shell:
ipset create NAME hash:ip
NAMEis the name of the collection.
hash:ipis the method of storing and searching the collection. Mainly 2 types are used:
hash:ipfor a collection of individual IPs and
hash:netfor a collection of networks. The difference is how efficient the storage of the collection will be and how fast the kernel will search in the collection for matching packets.
To see the active collections, run:
ipset list -n
-n is required to show just the names. Without it,
ipset will also dump the entire collection.
To add IPs to our collection, run:
ipset add NAME 220.127.116.11
to delete IPs from our collection, run:
ipset del NAME 18.104.22.168
Check the manual page of
ipset for more information.
FireHOL support for
ipset has two aspects:
FireHOL can use ipset collections for matching packets in all its statements. They are part of the
dst keywords. For example, to allow smtp requests from all the clients in a collection, use:
server smtp accept src ipset:NAME
To all the servers IPs of a collection:
server smtp accept dst ipset:NAME
Matching both clients' and servers' IPs is also possible:
server smtp accept src ipset:NAME dst ipset:NAME
You can actually use
ipset:NAME like an IP, in all statements:
blacklist full ipset:BADGUYS ... transparent_squid 3128 "root squid proxy" inface eth0 \ src ipset:mylans \ dst not ipset:servers_that_dont_like_proxies ... mark 1 OUTPUT dst "ipset:NAME 22.214.171.124" ... server smtp accept src "126.96.36.199 ipset:NAME1 ipset:NAME2" \ dst not "ipset:NAME3 188.8.131.52 ipset:NAME4 10.1.2.3"
The good thing about
ipset is that you can manipulate the IPs without restarting the firewall. Just add or remove IPs or networks with the
ipset command, and immediately the firewall will use the new IPs.
The bad thing is that the
ipset collection must exist before activating the firewall. This is why FireHOL can initialize the
ipset collections for you:
FireHOL has an
ipset helper. It is a wrapper around the real
ipset command and is handled internally within FireHOL in such a way so that the ipset collections defined in the configuration will be activated before activating the firewall.
FireHOL is also smart enough to restore the ipsets after a reboot, before it restores the firewall, so that everything will work as seamlessly as possible.
ipset helper has the same syntax with the real
ipset command. So in FireHOL you just add the
ipset statements you need, and FireHOL will do the rest.
Keep in mind that each
ipset collection is either IPv4 or IPv6. In FireHOL prefix
ipset with either
ipv6 and FireHOL will choose the right IP version.
The FireHOL helper also allows mass import of ipset collections from files. This is done with
ipset addfile command. This command is only supported from within
firehol.conf. It will not work on your terminal.
ipset addfile command will get a filename, remove all comments (anything after a
# on the same line), trim any empty lines and spaces, and add all the remaining lines to
ipset, as if each line of the file was run as
ipset add COLLECTION_NAME IP_FROM_FILE [other options].
The syntax of the
ipset addfile command is:
ipset addfile COLLECTION_NAME [ip|net] filename [other ipset add options]
COLLECTION_NAMEis the collection to add the IPs
ipwill select all the lines of the file that do not contain a
netwill select all the lines of the file that contain a
filenameis the filename to read. You can give relative filenames to
other ipset add optionsis whatever else
ipset addsupport that you are willing to give for each line
ipv4 ipset create badguys hash:ip ipv4 ipset add badguys 184.108.40.206 ipv4 ipset addfile badguys file-with-the-bad-guys-ips.txt ... ipv4 blacklist full ipset:badguys
ipset add command implemented in FireHOL also allows you to give multiple IPs separated by comma or enclosed in quotes and separated by space. This will also not work on your terminal.
ipv4 ipset create badguys hash:ip ipv4 ipset add badguys 220.127.116.11,18.104.22.168,22.214.171.124 # << comma separated ipv4 ipset add badguys "126.96.36.199 188.8.131.52" # << space separated in quotes
The url http://rules.emergingthreats.net/fwrules/emerging-Block-IPs.txt contains a list of IPs that we would like to block.
Get this file to
cd /etc/firehol wget "http://rules.emergingthreats.net/fwrules/emerging-Block-IPs.txt"
/etc/firehol/firehol.conf and add these:
# one collection for the single IPs ipv4 ipset create emerging_block_ips hash:ip ipv4 ipset addfile emerging_block_ips ips emerging-Block-IPs.txt # another collection for the networks ipv4 ipset create emerging_block_nets hash:net ipv4 ipset addfile emerging_block_nets nets emerging-Block-IPs.txt # blacklist them ipv4 blacklist full ipset:emerging_block_ips ipset:emerging_block_nets
Now, create a small script to update it daily:
#!/bin/bash tmp=$(mktemp) || exit 1 wget -O $tmp "http://rules.emergingthreats.net/fwrules/emerging-Block-IPs.txt" if [ $? -ne 0 -o ! -s $tmp ] then rm $tmp echo >&2 "Cannot download blacklist." exit 1 fi # update the ipsets firehol ipset_update_from_file emerging_block_ips ips $tmp firehol ipset_update_from_file emerging_block_nets nets $tmp rm $tmp
As you can see we called FireHOL, but this just updates the IPs in the ipsets. It does not touch the firewall. After the
ipset_update_from_file parameter, FireHOL accepts everything
ipset addfile accepts.