[fix] Revert "fix: check if the browser supports Sec-Fetch headers (#4696)"

Many bots will probably use other user agents than the common ones (or rotate
different ones)[1].

On my instance I can observe how bots with other UA headers are no longer
stopped with the patch of PR #4696.

This reverts PR #4696 commit 19b116f1d7.

[1] https://github.com/searxng/searxng/pull/4696#pullrequestreview-2806695481
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/botdetection/http_sec_fetch.py

@@ -28,7 +28,6 @@ from ipaddress import (
     IPv6Network,
 )
 
-import re
 import flask
 import werkzeug
 
@@ -38,44 +37,6 @@ from . import config
 from ._helpers import logger
 
 
-def is_browser_supported(user_agent: str) -> bool:
-    """Check if the browser supports Sec-Fetch headers.
-
-    https://caniuse.com/mdn-http_headers_sec-fetch-dest
-    https://caniuse.com/mdn-http_headers_sec-fetch-mode
-    https://caniuse.com/mdn-http_headers_sec-fetch-site
-
-    Supported browsers:
-    - Chrome >= 80
-    - Firefox >= 90
-    - Safari >= 16.4
-    - Edge (mirrors Chrome)
-    - Opera (mirrors Chrome)
-    """
-    user_agent = user_agent.lower()
-
-    # Chrome/Chromium/Edge/Opera
-    chrome_match = re.search(r'chrome/(\d+)', user_agent)
-    if chrome_match:
-        version = int(chrome_match.group(1))
-        return version >= 80
-
-    # Firefox
-    firefox_match = re.search(r'firefox/(\d+)', user_agent)
-    if firefox_match:
-        version = int(firefox_match.group(1))
-        return version >= 90
-
-    # Safari
-    safari_match = re.search(r'version/(\d+)\.(\d+)', user_agent)
-    if safari_match:
-        major = int(safari_match.group(1))
-        minor = int(safari_match.group(2))
-        return major > 16 or (major == 16 and minor >= 4)
-
-    return False
-
-
 def filter_request(
     network: IPv4Network | IPv6Network,
     request: SXNG_Request,
@@ -88,11 +49,8 @@ def filter_request(
         )
         return None
 
-    # Only check Sec-Fetch headers for supported browsers
-    user_agent = request.headers.get('User-Agent', '')
-    if is_browser_supported(user_agent):
     val = request.headers.get("Sec-Fetch-Mode", "")
-        if val not in ('navigate', 'cors'):
+    if val != "navigate":
         logger.debug("invalid Sec-Fetch-Mode '%s'", val)
         return flask.redirect(flask.url_for('index'), code=302)
 
@@ -102,7 +60,7 @@ def filter_request(
         flask.redirect(flask.url_for('index'), code=302)
 
     val = request.headers.get("Sec-Fetch-Dest", "")
-        if val not in ('document', 'empty'):
+    if val != "document":
         logger.debug("invalid Sec-Fetch-Dest '%s'", val)
         flask.redirect(flask.url_for('index'), code=302)