Minifirewall

Minifirewall is shellscripts for easy firewalling on a standalone server we used netfilter/iptables http://netfilter.org/ designed for recent Linux kernel See https://gitea.evolix.org/evolix/minifirewall

Install

install --mode 0700 minifirewall /etc/init.d/minifirewall
install --mode 0600 minifirewall.conf /etc/default/minifirewall
mkdir --mode 0700 /etc/minifirewall.d

Config

Edit /etc/default/minifirewall file:

• If your interface is not eth0, change INT variable
• If you don't use IPv6, set IPv6='off'
• Modify INTLAN variable, probably with your <IP>/32 or your local network if you trust it
• Set your trusted and privilegied IP addresses in TRUSTEDIPS and PRIVILEGIEDIPS variables
• Authorize your public services with SERVICESTCP1 and SERVICESUDP1 variables
• Authorize your semi-public services (only for TRUSTEDIPS and PRIVILEGIEDIPS ) with SERVICESTCP2 and SERVICESUDP2 variables
• Authorize your private services (only for TRUSTEDIPS ) with SERVICESTCP3 and SERVICESUDP3 variables
• Configure your authorizations for external services : DNS, HTTP, HTTPS, SMTP, SSH, NTP
• Add your specific rules

Docker

To use minifirewall with Docker you must to change the variable DOCKER='on' By default, exposed services won't be reachable outside the host.

If you need to allow/deny access to outside hosts, you can rely on the chain MINIFW-DOCKER-INPUT-MANUAL Note : this chain is only crossed by incoming 'tcp syn' packets.

Examples :

# Open publicly the docker service exposed on port 80
/sbin/iptables -I MINIFW-DOCKER-INPUT-MANUAL -p tcp -m conntrack --ctorigdstport 80 -j RETURN

# Open to 192.0.2.0/24 the docker service exposed on port 22
/sbin/iptables -I MINIFW-DOCKER-INPUT-MANUAL -p tcp -s 192.0.2.0/24 -m conntrack --ctorigdstport 22 -j RETURN

# Block 192.0.2.42 access the docker service exposed on port 22
/sbin/iptables -I MINIFW-DOCKER-INPUT-MANUAL -p tcp -s 192.0.2.42 -m conntrack --ctorigdstport 80 -j DROP

Also, in DOCKER='on', host services will be reachable to the containers that are connected on the default bridge (docker0). From the container, you can reach them at 172.17.0.1 (unless docker0 has a different IP).

Ensure that your services listen on either 0.0.0.0 or 172.17.0.1/docker0. Keep in mind that some services may require you to allow the containers IP ranges (Postfix, PostgreSQL,...) For this case, you can allow 172.16.0.0/12

If you use different docker network bridge, you'll need to add rules for your network. You can use this one

# Accept all trafic from 172.16.0.0/12 (RFC1918) to reach 172.17.0.1
/sbin/iptables -I INPUT -p tcp --sport 1024:65535 -s 172.16.0.0/12 -d 172.17.0.1 -j ACCEPT

If you want to have fine-grained rules for controling the communication from containers to the host services, you can set DOCKER='manual'. This way, no rules allowing communication from containers host services are created.

You can then create your own set of rules.

# Allow the containers to reach PostgreSQL (5432/tcp) on 172.17.0.1
/sbin/iptables -I INPUT -p tcp --sport 1024:65535 --dport 5432 -s 172.16.0.0/12 -d 172.17.0.1 -j ACCEPT

Usage

/etc/init.d/minifirewall start/stop/restart

If you want to add minifirewall in boot sequence, add the start command to /usr/share/scripts/alert5.

License

This is an Evolix project and is licensed under the GPLv3, see the LICENSE file for details.