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[mod] Shuffle httpx's default ciphers of a SSL context randomly.

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From the analyse of @9Ninety [1] we know that DDG (and may be other engines / I
have startpage in mind) does some kind of TLS fingerprint to block bots.

This patch shuffles the default ciphers from httpx to avoid a cipher profile
that is known to httpx (and blocked by DDG).

[1] https://github.com/searxng/searxng/issues/2246#issuecomment-1467895556

----

From `What Is TLS Fingerprint and How to Bypass It`_

> When implementing TLS fingerprinting, servers can't operate based on a
> locked-in whitelist database of fingerprints.  New fingerprints appear
> when web clients or TLS libraries release new versions. So, they have to
> live off a blocklist database instead.
> ...
> It's safe to leave the first three as is but shuffle the remaining ciphers
> and you can bypass the TLS fingerprint check.

.. _What Is TLS Fingerprint and How to Bypass It:
   https://www.zenrows.com/blog/what-is-tls-fingerprint#how-to-bypass-tls-fingerprinting

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
Closes: https://github.com/searxng/searxng/issues/2246
This commit is contained in:
Markus Heiser 2023-03-19 10:47:49 +01:00
parent 677903c355
commit 8fa54ffddf
1 changed files with 25 additions and 0 deletions
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25
searx/network/client.py
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@ -4,6 +4,7 @@
import asyncio
import logging
import random
from ssl import SSLContext
import threading
from typing import Any, Dict
@ -28,10 +29,34 @@ LOOP = None
SSLCONTEXTS: Dict[Any, SSLContext] = {}
def shuffle_ciphers(ssl_context):
"""Shuffle httpx's default ciphers of a SSL context randomly.
From `What Is TLS Fingerprint and How to Bypass It`_
> When implementing TLS fingerprinting, servers can't operate based on a
> locked-in whitelist database of fingerprints. New fingerprints appear
> when web clients or TLS libraries release new versions. So, they have to
> live off a blocklist database instead.
> ...
> It's safe to leave the first three as is but shuffle the remaining ciphers
> and you can bypass the TLS fingerprint check.
.. _What Is TLS Fingerprint and How to Bypass It:
https://www.zenrows.com/blog/what-is-tls-fingerprint#how-to-bypass-tls-fingerprinting
"""
c_list = httpx._config.DEFAULT_CIPHERS.split(':') # pylint: disable=protected-access
sc_list, c_list = c_list[:3], c_list[3:]
random.shuffle(c_list)
ssl_context.set_ciphers(":".join(sc_list + c_list))
def get_sslcontexts(proxy_url=None, cert=None, verify=True, trust_env=True, http2=False):
key = (proxy_url, cert, verify, trust_env, http2)
if key not in SSLCONTEXTS:
SSLCONTEXTS[key] = httpx.create_ssl_context(cert, verify, trust_env, http2)
shuffle_ciphers(SSLCONTEXTS[key])
return SSLCONTEXTS[key]