90 lines
2.8 KiB
Python
90 lines
2.8 KiB
Python
"""Fragment-based DPI bypass strategy.
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Splits the real TLS ClientHello into fragments so that DPI systems
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that only inspect the first packet or don't reassemble TCP streams
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cannot read the SNI.
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"""
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import asyncio
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import socket
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import time
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from typing import Optional
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from .base import BypassStrategy
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from ..tls.fragment import fragment_client_hello
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class FragmentBypass(BypassStrategy):
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"""Bypass DPI by fragmenting the TLS ClientHello.
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This is the most compatible cross-platform bypass method.
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It works by splitting the ClientHello into multiple TCP segments,
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with the split point strategically placed in the middle of the
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SNI extension value.
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DPI systems that don't reassemble TCP streams will see an incomplete
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SNI in the first packet and won't be able to filter it.
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"""
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name = "fragment"
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def __init__(
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self,
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strategy: str = "sni_split",
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fragment_delay: float = 0.1,
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tcp_nodelay: bool = True,
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):
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"""Initialize fragment bypass.
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Args:
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strategy: Fragmentation strategy (sni_split, half, multi, tls_record_frag)
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fragment_delay: Delay between fragments in seconds
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tcp_nodelay: Enable TCP_NODELAY to send fragments immediately
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"""
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self.strategy = strategy
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self.fragment_delay = fragment_delay
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self.tcp_nodelay = tcp_nodelay
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async def apply(
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self,
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client_sock: socket.socket,
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server_sock: socket.socket,
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fake_sni: str,
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first_data: bytes,
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loop=None,
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) -> bool:
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"""Apply fragmentation to the first TLS record.
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The first_data from the client (usually a TLS ClientHello) is
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fragmented and sent to the server in multiple TCP segments.
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"""
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if loop is None:
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loop = asyncio.get_running_loop()
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try:
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# Enable TCP_NODELAY so each send() becomes its own segment
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if self.tcp_nodelay:
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server_sock.setsockopt(
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socket.IPPROTO_TCP, socket.TCP_NODELAY, 1
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)
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# Fragment the ClientHello
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fragments = fragment_client_hello(first_data, self.strategy)
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# Send each fragment as a separate TCP segment
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for i, fragment in enumerate(fragments):
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await loop.sock_sendall(server_sock, fragment)
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if i < len(fragments) - 1 and self.fragment_delay > 0:
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await asyncio.sleep(self.fragment_delay)
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# Disable TCP_NODELAY after fragments are sent (optional)
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if self.tcp_nodelay:
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server_sock.setsockopt(
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socket.IPPROTO_TCP, socket.TCP_NODELAY, 0
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)
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return True
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except Exception:
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return False
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