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247 lines
7 KiB
Python
247 lines
7 KiB
Python
# SPDX-License-Identifier: AGPL-3.0-or-later
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"""Bot protection / IP rate limitation. The intention of rate limitation is to
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limit suspicious requests from an IP. The motivation behind this is the fact
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that SearXNG passes through requests from bots and is thus classified as a bot
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itself. As a result, the SearXNG engine then receives a CAPTCHA or is blocked
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by the search engine (the origin) in some other way.
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To avoid blocking, the requests from bots to SearXNG must also be blocked, this
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is the task of the limiter. To perform this task, the limiter uses the methods
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from the :ref:`botdetection`:
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- Analysis of the HTTP header in the request / :ref:`botdetection probe headers`
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can be easily bypassed.
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- Block and pass lists in which IPs are listed / :ref:`botdetection ip_lists`
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are hard to maintain, since the IPs of bots are not all known and change over
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the time.
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- Detection & dynamically :ref:`botdetection rate limit` of bots based on the
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behavior of the requests. For dynamically changeable IP lists a Redis
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database is needed.
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The prerequisite for IP based methods is the correct determination of the IP of
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the client. The IP of the client is determined via the X-Forwarded-For_ HTTP
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header.
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.. attention::
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A correct setup of the HTTP request headers ``X-Forwarded-For`` and
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``X-Real-IP`` is essential to be able to assign a request to an IP correctly:
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- `NGINX RequestHeader`_
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- `Apache RequestHeader`_
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.. _X-Forwarded-For:
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https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-For
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.. _NGINX RequestHeader:
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https://docs.searxng.org/admin/installation-nginx.html#nginx-s-searxng-site
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.. _Apache RequestHeader:
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https://docs.searxng.org/admin/installation-apache.html#apache-s-searxng-site
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Enable Limiter
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==============
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To enable the limiter activate:
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.. code:: yaml
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server:
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...
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limiter: true # rate limit the number of request on the instance, block some bots
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and set the redis-url connection. Check the value, it depends on your redis DB
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(see :ref:`settings redis`), by example:
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.. code:: yaml
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redis:
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url: unix:///usr/local/searxng-redis/run/redis.sock?db=0
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Configure Limiter
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=================
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The methods of :ref:`botdetection` the limiter uses are configured in a local
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file ``/etc/searxng/limiter.toml``. The defaults are shown in limiter.toml_ /
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Don't copy all values to your local configuration, just enable what you need by
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overwriting the defaults. For instance to activate the ``link_token`` method in
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the :ref:`botdetection.ip_limit` you only need to set this option to ``true``:
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.. code:: toml
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[botdetection.ip_limit]
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link_token = true
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.. _limiter.toml:
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``limiter.toml``
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================
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In this file the limiter finds the configuration of the :ref:`botdetection`:
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- :ref:`botdetection ip_lists`
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- :ref:`botdetection rate limit`
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- :ref:`botdetection probe headers`
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.. kernel-include:: $SOURCEDIR/limiter.toml
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:code: toml
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Implementation
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==============
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"""
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from __future__ import annotations
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import sys
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from pathlib import Path
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from ipaddress import ip_address
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import flask
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import werkzeug
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from searx import (
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logger,
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redisdb,
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)
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from searx import botdetection
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from searx.botdetection import (
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config,
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http_accept,
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http_accept_encoding,
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http_accept_language,
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http_user_agent,
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ip_limit,
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ip_lists,
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get_network,
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get_real_ip,
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dump_request,
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)
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# the configuration are limiter.toml and "limiter" in settings.yml so, for
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# coherency, the logger is "limiter"
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logger = logger.getChild('limiter')
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CFG: config.Config = None # type: ignore
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_INSTALLED = False
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LIMITER_CFG_SCHEMA = Path(__file__).parent / "limiter.toml"
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"""Base configuration (schema) of the botdetection."""
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LIMITER_CFG = Path('/etc/searxng/limiter.toml')
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"""Local Limiter configuration."""
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CFG_DEPRECATED = {
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# "dummy.old.foo": "config 'dummy.old.foo' exists only for tests. Don't use it in your real project config."
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}
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def get_cfg() -> config.Config:
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global CFG # pylint: disable=global-statement
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if CFG is None:
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CFG = config.Config.from_toml(LIMITER_CFG_SCHEMA, LIMITER_CFG, CFG_DEPRECATED)
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return CFG
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def filter_request(request: flask.Request) -> werkzeug.Response | None:
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# pylint: disable=too-many-return-statements
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cfg = get_cfg()
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real_ip = ip_address(get_real_ip(request))
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network = get_network(real_ip, cfg)
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if request.path == '/healthz':
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return None
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# link-local
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if network.is_link_local:
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return None
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# block- & pass- lists
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#
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# 1. The IP of the request is first checked against the pass-list; if the IP
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# matches an entry in the list, the request is not blocked.
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# 2. If no matching entry is found in the pass-list, then a check is made against
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# the block list; if the IP matches an entry in the list, the request is
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# blocked.
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# 3. If the IP is not in either list, the request is not blocked.
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match, msg = ip_lists.pass_ip(real_ip, cfg)
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if match:
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logger.warning("PASS %s: matched PASSLIST - %s", network.compressed, msg)
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return None
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match, msg = ip_lists.block_ip(real_ip, cfg)
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if match:
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logger.error("BLOCK %s: matched BLOCKLIST - %s", network.compressed, msg)
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return flask.make_response(('IP is on BLOCKLIST - %s' % msg, 429))
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# methods applied on /
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for func in [
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http_user_agent,
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]:
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val = func.filter_request(network, request, cfg)
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if val is not None:
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return val
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# methods applied on /search
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if request.path == '/search':
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for func in [
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http_accept,
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http_accept_encoding,
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http_accept_language,
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http_user_agent,
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ip_limit,
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]:
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val = func.filter_request(network, request, cfg)
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if val is not None:
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return val
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logger.debug(f"OK {network}: %s", dump_request(flask.request))
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return None
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def pre_request():
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"""See :py:obj:`flask.Flask.before_request`"""
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return filter_request(flask.request)
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def is_installed():
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"""Returns ``True`` if limiter is active and a redis DB is available."""
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return _INSTALLED
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def initialize(app: flask.Flask, settings):
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"""Install the limiter"""
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global _INSTALLED # pylint: disable=global-statement
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# even if the limiter is not activated, the botdetection must be activated
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# (e.g. the self_info plugin uses the botdetection to get client IP)
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cfg = get_cfg()
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redis_client = redisdb.client()
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botdetection.init(cfg, redis_client)
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if not (settings['server']['limiter'] or settings['server']['public_instance']):
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return
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if not redis_client:
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logger.error(
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"The limiter requires Redis, please consult the documentation: "
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"https://docs.searxng.org/admin/searx.limiter.html"
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)
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if settings['server']['public_instance']:
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sys.exit(1)
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return
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_INSTALLED = True
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if settings['server']['public_instance']:
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# overwrite limiter.toml setting
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cfg.set('botdetection.ip_limit.link_token', True)
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app.before_request(pre_request)
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