mirror of
https://github.com/searxng/searxng.git
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108 lines
3.0 KiB
Python
108 lines
3.0 KiB
Python
# SPDX-License-Identifier: AGPL-3.0-or-later
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"""
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Method ``http_sec_fetch``
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-------------------------
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The ``http_sec_fetch`` method protect resources from web attacks with `Fetch
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Metadata`_. A request is filtered out in case of:
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- http header Sec-Fetch-Mode_ is invalid
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- http header Sec-Fetch-Dest_ is invalid
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.. _Fetch Metadata:
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https://developer.mozilla.org/en-US/docs/Glossary/Fetch_metadata_request_header
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.. _Sec-Fetch-Dest:
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https://developer.mozilla.org/en-US/docs/Web/API/Request/destination
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.. _Sec-Fetch-Mode:
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https://developer.mozilla.org/en-US/docs/Web/API/Request/mode
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"""
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# pylint: disable=unused-argument
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from ipaddress import (
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IPv4Network,
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IPv6Network,
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)
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import re
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import flask
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import werkzeug
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from . import config
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from ._helpers import logger
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def is_browser_supported(user_agent: str) -> bool:
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"""Check if the browser supports Sec-Fetch headers.
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https://caniuse.com/mdn-http_headers_sec-fetch-dest
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https://caniuse.com/mdn-http_headers_sec-fetch-mode
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https://caniuse.com/mdn-http_headers_sec-fetch-site
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Supported browsers:
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- Chrome >= 80
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- Firefox >= 90
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- Safari >= 16.4
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- Edge (mirrors Chrome)
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- Opera (mirrors Chrome)
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"""
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user_agent = user_agent.lower()
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# Chrome/Chromium/Edge/Opera
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chrome_match = re.search(r'chrome/(\d+)', user_agent)
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if chrome_match:
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version = int(chrome_match.group(1))
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return version >= 80
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# Firefox
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firefox_match = re.search(r'firefox/(\d+)', user_agent)
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if firefox_match:
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version = int(firefox_match.group(1))
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return version >= 90
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# Safari
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safari_match = re.search(r'version/(\d+)\.(\d+)', user_agent)
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if safari_match:
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major = int(safari_match.group(1))
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minor = int(safari_match.group(2))
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return major > 16 or (major == 16 and minor >= 4)
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return False
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def filter_request(
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network: IPv4Network | IPv6Network,
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request: flask.Request,
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cfg: config.Config,
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) -> werkzeug.Response | None:
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if not request.is_secure:
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logger.warning(
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"Sec-Fetch cannot be verified for non-secure requests (HTTP headers are not set/sent by the client)."
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)
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return None
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# Only check Sec-Fetch headers for supported browsers
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user_agent = request.headers.get('User-Agent', '')
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if is_browser_supported(user_agent):
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val = request.headers.get("Sec-Fetch-Mode", "")
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if val not in ('navigate', 'cors'):
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logger.debug("invalid Sec-Fetch-Mode '%s'", val)
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return flask.redirect(flask.url_for('index'), code=302)
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val = request.headers.get("Sec-Fetch-Site", "")
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if val not in ('same-origin', 'same-site', 'none'):
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logger.debug("invalid Sec-Fetch-Site '%s'", val)
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flask.redirect(flask.url_for('index'), code=302)
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val = request.headers.get("Sec-Fetch-Dest", "")
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if val not in ('document', 'empty'):
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logger.debug("invalid Sec-Fetch-Dest '%s'", val)
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flask.redirect(flask.url_for('index'), code=302)
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return None
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