1.9 KiB
iblock
iblock is an inetd program adding the client IP to a Packet Filter table.
It is meant to be used to block scanner connecting on unused ports.
Upon connection, the IP is added to a PF table and all established connections with this IP are killed. You need to use a PF bloking rule using the table.
How to use
Add a dedicated user
useradd -s /sbin/nologin _iblock
Configure doas
Add in /etc/doas.conf:
permit nopass _iblock cmd /sbin/pfctl
Configure inetd
Start inetd service with this in /etc/inetd.conf:
666 stream tcp nowait _iblock /usr/local/bin/iblock iblock
666 stream tcp6 nowait _iblock /usr/local/bin/iblock iblock
You can change the PF table by adding it as a parameter like this:
In this example, the parameter blocklist will add IPs to the blocklist PF table.
666 stream tcp nowait _iblock /usr/local/bin/iblock iblock blocklist
666 stream tcp6 nowait _iblock /usr/local/bin/iblock iblock blocklist
Default is "iblocked" table.
Configure packet filter
Use this in /etc/pf.conf, choose which ports will trigger the ban from the variable:
# services triggering a block
blocking_tcp="{ 21 23 53 111 135 137:139 445 1433 25565 5432 3389 3306 27019 }"
table <blocked> persist
block in quick from <blocked> label iblock
pass in quick on egress inet proto tcp to port $blocking_tcp rdr-to 127.0.0.1 port 666
pass in quick on egress inet6 proto tcp to port $blocking_tcp rdr-to ::1 port 666
Don't forget to reload the rules with pfctl -f /etc/pf.conf.
Get some statistics
Done! You can see IP banned using pfctl -t blocked -T show and iBlock will send blocked addresses to syslog.
In the example I added a label to the block rule, you can use pfctl -s labels to view statistics from this rule, see documentation for column meaning.
TODO
- A proper man page