searxng/docs/admin/filtron.rst

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How to protect an instance
==========================
Searx depens 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. Information on how to install it can be found at the `project page of filtron <https://github.com/asciimoo/filtron>`__.
Sample configuration of filtron
-------------------------------
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":"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":"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":"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":"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":"block",
"params":{
"message":"Rate limit exceeded"
}
}
]
}
]
}]
Route request through filtron
-----------------------------
Filtron can be started using the following command:
.. code:: bash
$ 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_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;
proxy_pass http://127.0.0.1:4004/;
}
Requests are coming from port 4004 going through filtron and then forwarded to port 8888 where a searx is being run.