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@@ -0,0 +1,114 @@
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+How to protect an instance
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+==========================
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+
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+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.
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+
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+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>`__.
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+
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+Sample configuration of filtron
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+-------------------------------
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+
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+An example configuration can be find below. This configuration limits the access of
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+
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+ * scripts or applications (roboagent limit)
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+
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+ * webcrawlers (botlimit)
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+
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+ * IPs which send too many requests (IP limit)
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+
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+ * too many json, csv, etc. requests (rss/json limit)
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+
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+ * the same UserAgent of if too many requests (useragent limit)
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+
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+
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+.. code:: json
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+
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+ [
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+ {
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+ "name": "search request",
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+ "filters": ["Param:q", "Path=^(/|/search)$"],
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+ "interval": <time-interval-in-sec>,
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+ "limit": <max-request-number-in-interval>,
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+ "subrules": [
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+ {
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+ "name": "roboagent limit",
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+ "interval": <time-interval-in-sec>,
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+ "limit": <max-request-number-in-interval>,
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+ "filters": ["Header:User-Agent=(curl|cURL|Wget|python-requests|Scrapy|FeedFetcher|Go-http-client)"],
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+ "actions": [
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+ {"name": "block",
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+ "params": {"message": "Rate limit exceeded"}}
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+ ]
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+ },
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+ {
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+ "name": "botlimit",
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+ "limit": 0,
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+ "stop": true,
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+ "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)"],
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+ "actions": [
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+ {"name": "block",
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+ "params": {"message": "Rate limit exceeded"}}
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+ ]
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+ },
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+ {
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+ "name": "IP limit",
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+ "interval": <time-interval-in-sec>,
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+ "limit": <max-request-number-in-interval>,
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+ "stop": true,
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+ "aggregations": ["Header:X-Forwarded-For"],
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+ "actions": [
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+ {"name": "block",
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+ "params": {"message": "Rate limit exceeded"}}
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+ ]
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+ },
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+ {
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+ "name": "rss/json limit",
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+ "interval": <time-interval-in-sec>,
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+ "limit": <max-request-number-in-interval>,
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+ "stop": true,
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+ "filters": ["Param:format=(csv|json|rss)"],
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+ "actions": [
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+ {"name": "block",
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+ "params": {"message": "Rate limit exceeded"}}
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+ ]
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+ },
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+ {
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+ "name": "useragent limit",
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+ "interval": <time-interval-in-sec>,
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+ "limit": <max-request-number-in-interval>,
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+ "aggregations": ["Header:User-Agent"],
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+ "actions": [
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+ {"name": "block",
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+ "params": {"message": "Rate limit exceeded"}}
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+ ]
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+ }
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+ ]
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+ }
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+ ]
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+
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+
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+
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+Route request through filtron
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+-----------------------------
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+
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+Filtron can be started using the following command:
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+
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+.. code:: bash
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+
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+ $ filtron -rules rules.json
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+
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+It listens on 127.0.0.1:4004 and forwards filtered requests to 127.0.0.1:8888 by default.
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+
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+Use it along with ``nginx`` with the following example configuration.
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+
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+.. code:: bash
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+
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+ location / {
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+ proxy_set_header Host $http_host;
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+ proxy_set_header X-Real-IP $remote_addr;
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+ proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
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+ proxy_set_header X-Scheme $scheme;
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+ proxy_pass http://127.0.0.1:4004/;
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+ }
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+
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+Requests are coming from port 4004 going through filtron and then forwarded to port 8888 where a searx is being run.
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Noémi Ványi