dnsfilter

It's simple DNS proxy filter server with configurable blacklist based on twisted framework for study projects (NOT for production).

Requirements

python2 (version 2.7) and twisted (version 16.5.0)
It's strongly recommended to install inside isolated virtual environment!
More details http://docs.python-guide.org/en/latest/dev/virtualenvs/.
You need root to start dnsfilter on TCP/UDP port 53 (default setting for dnsfilter).

Initial Setup:

you can check if port 53 is free by:

1. run check_port.py (you need root to execute it), f.e

    $ sudo python2 check_port.py  

    $ sudo lsof -i:53  

Usually, system service/dns server uses it.
In my scenario, in Ubuntu systemd-resolved and dnsmasq server is on port 53.
To disbale it:
1)

    $ sudo service systemd-resolved stop  

2. edit /etc/NetworkManager/NetworkManager.conf and comment out the line dns=dnsmasq to have line, like:

    #dns=dnsmasq  

restart Network-Manager

    $ sudo restart network-manager  

or

    $ sudo service network-manager restart  

You can start web - server to get html page with specified answer if it's query for restricted domain names (you can edit this page in json.conf): You can use any web-server, but you need root to start it on port 80.

1. F.e, default python http-server (index.html and stop_page.jpg should be in same folder you start server)

    $ sudo python -m http.server 80

2. or twisted web - server (if you using virtual environment you should indicate path to twisted)

    $ sudo /home/username/path/to/virtual_env/bin/twistd web --port tcp:80 --path=.

it will start twisted server, which is at /home/username/path/to/virtual_env/bin/twistd and will use current folder as root for server.

Editing json.conf

Create blacklist:
You can add restricted domain names in json.conf , like 'name1, 'name2' etc, separated by comma:

    "blacklist":["vk.com", "odnoklassniki.ru"]  

You can also:

• specify DNS servers for response if query is not restricted
  Google DNS servers are default.
• starting/disabling logs for all queries or restricted only
  Please be careful if you are using logging for all queries due to big amount of data
• different options for index.html

Running dnsfilter:

    $ sudo /home/username/path/to/virtual_env/bin/python dnsfilter.py

Running test:

'127.0.0.1' is default address for restricted queries.
You can check if all restricted queries from blacklist is redirected to it.

    $ python test.py