
.. _searx filtron:

==========================
How to protect an instance
==========================

.. sidebar:: further reading

   - :ref:`filtron.sh`
   - :ref:`nginx searx site`


.. contents:: Contents
   :depth: 2
   :local:
   :backlinks: entry

.. _filtron: https://github.com/asciimoo/filtron

Searx depends on external search services.  To avoid the abuse of these services
it is advised to limit the number of requests processed by searx.

An application firewall, filtron_ solves exactly this problem.  Filtron is just
a middleware between your web server (nginx, apache, ...) and searx, we describe
such infratructures in chapter: :ref:`architecture`.


filtron & go
============

.. _Go: https://golang.org/
.. _filtron README: https://github.com/asciimoo/filtron/blob/master/README.md

Filtron needs Go_ installed.  If Go_ is preinstalled, filtron_ is simply
installed by ``go get`` package management (see `filtron README`_).  If you use
filtron as middleware, a more isolated setup is recommended.  To simplify such
an installation and the maintenance of, use our script :ref:`filtron.sh`.

.. _Sample configuration of filtron:

Sample configuration of filtron
===============================

.. sidebar:: Tooling box

   - :origin:`/etc/filtron/rules.json <utils/templates/etc/filtron/rules.json>`

An example configuration can be find below. This configuration limits the access
of:

- scripts or applications (roboagent limit)
- webcrawlers (botlimit)
- IPs which send too many requests (IP limit)
- too many json, csv, etc. requests (rss/json limit)
- the same UserAgent of if too many requests (useragent limit)

.. code:: json

   [
     { "name": "search request",
       "filters": [
	 "Param:q",
	 "Path=^(/|/search)$"
       ],
       "interval": "<time-interval-in-sec (int)>",
       "limit": "<max-request-number-in-interval (int)>",
       "subrules": [
	 {
	   "name": "roboagent limit",
	   "interval": "<time-interval-in-sec (int)>",
	   "limit": "<max-request-number-in-interval (int)>",
	   "filters": [
	     "Header:User-Agent=(curl|cURL|Wget|python-requests|Scrapy|FeedFetcher|Go-http-client)"
	   ],
	   "actions": [
	     { "name": "log"},
	     { "name": "block",
	       "params": {
		 "message": "Rate limit exceeded"
	       }
	     }
	   ]
	 },
	 {
	   "name": "botlimit",
	   "limit": 0,
	   "stop": true,
	   "filters": [
	     "Header:User-Agent=(Googlebot|bingbot|Baiduspider|yacybot|YandexMobileBot|YandexBot|Yahoo! Slurp|MJ12bot|AhrefsBot|archive.org_bot|msnbot|MJ12bot|SeznamBot|linkdexbot|Netvibes|SMTBot|zgrab|James BOT)"
	   ],
	   "actions": [
	     { "name": "log"},
	     { "name": "block",
	       "params": {
		 "message": "Rate limit exceeded"
	       }
	     }
	   ]
	 },
	 {
	   "name": "IP limit",
	   "interval": "<time-interval-in-sec (int)>",
	   "limit": "<max-request-number-in-interval (int)>",
	   "stop": true,
	   "aggregations": [
	     "Header:X-Forwarded-For"
	   ],
	   "actions": [
	     { "name": "log"},
	     { "name": "block",
	       "params": {
		 "message": "Rate limit exceeded"
	       }
	     }
	   ]
	 },
	 {
	   "name": "rss/json limit",
	   "interval": "<time-interval-in-sec (int)>",
	   "limit": "<max-request-number-in-interval (int)>",
	   "stop": true,
	   "filters": [
	     "Param:format=(csv|json|rss)"
	   ],
	   "actions": [
	     { "name": "log"},
	     { "name": "block",
	       "params": {
		 "message": "Rate limit exceeded"
	       }
	     }
	   ]
	 },
	 {
	   "name": "useragent limit",
	   "interval": "<time-interval-in-sec (int)>",
	   "limit": "<max-request-number-in-interval (int)>",
	   "aggregations": [
	     "Header:User-Agent"
	   ],
	   "actions": [
	     { "name": "log"},
	     { "name": "block",
	       "params": {
		 "message": "Rate limit exceeded"
	       }
	     }
	   ]
	 }
       ]
     }
   ]


.. _filtron route request:

Route request through filtron
=============================

Filtron can be started using the following command:

.. code:: sh

   $ filtron -rules rules.json

It listens on ``127.0.0.1:4004`` and forwards filtered requests to
``127.0.0.1:8888`` by default.

Use it along with ``nginx`` with the following example configuration.

.. code:: nginx

   location / {
       proxy_pass         http://127.0.0.1:4004/;

       proxy_set_header   Host             $http_host;
       proxy_set_header   X-Real-IP        $remote_addr;
       proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for;
       proxy_set_header   X-Scheme         $scheme;
   }

Requests are coming from port 4004 going through filtron and then forwarded to
port 8888 where a searx is being run. For a complete setup see: :ref:`nginx
searx site`.
