PyWall

A Python firewall: Because slow networks are secure networks.

Installation

This section assumes that you are installing this program on Ubuntu 14.04 LTS.
This firewall should work on other Linux systems, but safety not guaranteed.

First, install the required packages. On Ubuntu, these are iptables, python,
python-pip, build-essential, python-dev, and
libnetfilter-queue-dev. Next, use pip2 to install the project dependencies,
which can be found in requirements.txt.

The commands for both these operations are:

sudo apt-get install python python-pip iptables build-essential python-dev libnetfilter-queue-dev
pip install --user -r requirements.txt

Running

The main file is main.py, which needs to be run as root to modify IPTables.
Additionally, main needs to receive a JSON configuration file as its first
argument. If running with the example configuration, the command is:

sudo python2 main.py examples/example.json

To stop PyWall, press Control-C.

Troubleshooting

PyWall should undo its changes to IPTables after exiting. However, if you are
unable to access the internet after exiting PyWall, view existing
IPTables rules with sudo iptables -nL. If a rule with the target chain
NFQueue lingers, delete it with
sudo iptables -D INPUT -j NFQUEUE --queue-num [undesired-queue-number].

For INPUT rules, the command is sudo iptables -D INPUT -j NFQUEUE --queue-num 1.
For OUTPUT rules, the command is sudo iptables -D OUTPUT -j NFQUEUE --queue-num 2.

In case PyWall gives a message that another application has the xtables lock,
Control-C the server, ensure that all the IPTables rules are cleared, and
restart PyWall.