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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 asyncio
import logging import logging
import random
from ssl import SSLContext from ssl import SSLContext
import threading import threading
from typing import Any, Dict from typing import Any, Dict
@ -28,10 +29,34 @@ LOOP = None
SSLCONTEXTS: Dict[Any, SSLContext] = {} 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): def get_sslcontexts(proxy_url=None, cert=None, verify=True, trust_env=True, http2=False):
key = (proxy_url, cert, verify, trust_env, http2) key = (proxy_url, cert, verify, trust_env, http2)
if key not in SSLCONTEXTS: if key not in SSLCONTEXTS:
SSLCONTEXTS[key] = httpx.create_ssl_context(cert, verify, trust_env, http2) SSLCONTEXTS[key] = httpx.create_ssl_context(cert, verify, trust_env, http2)
shuffle_ciphers(SSLCONTEXTS[key])
return SSLCONTEXTS[key] return SSLCONTEXTS[key]