From ee04ff6e6da5cb44d05fa3cfdda6e903285d0bac Mon Sep 17 00:00:00 2001
From: Sunpy <sunpy@osufx.com>
Date: Sun, 19 Mar 2023 06:02:55 +0100
Subject: [PATCH] Added 0.3.7 obfuscation layer

---
 sampy/network/game.py | 63 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/sampy/network/game.py b/sampy/network/game.py
index 38c12b8..7b4cddd 100644
--- a/sampy/network/game.py
+++ b/sampy/network/game.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import logging
 from typing import TYPE_CHECKING, Tuple
 
 if TYPE_CHECKING:
@@ -9,4 +10,66 @@ if TYPE_CHECKING:
 class Game:
     @staticmethod
     async def on_packet(server: Server, packet: bytes, addr: Tuple[str, int]) -> bool:
+        packet = Obfuscation.deobfuscate(server, packet)
+
+        # TODO
         return False
+
+
+class Obfuscation:
+    # Found @ addr 0x004C88E0 in windows server executable
+    LOOKUP_TABLE = bytes.fromhex(
+        """
+        b46207e59daf63dde3d0ccfedcdb6b2e6a40ab47c9d153d52091a50e4adf1889
+        fd6f2512b713770065366d49ec572aa9115ffa7895a4bd1ed97944cdde81eb09
+        3ef6eeda7fa31aa72da6adc14693d21b9caad74e4b4d4cf3b834c0ca88f494cb
+        04393082d673b0bf2201416e482ca875b10aae9f278010cef02928850d05f735
+        bbbc1506f56071031fea5a33928de7905be9cf9ed35ded311c0b5216510f86c5
+        689b210c8b4287ff4fbec8e8c7d47ae0552f8a8eba9837e4b238a1b632833a7b
+        843c61fb8c143d433b1dc3a296b3f8c4f2262bd87cfc232466ef6964505459f1
+        a074acc67db5e6e2c27e67175ee1b93f6c700899455676f99a9719725c028f58
+        """
+    )
+
+    # I think this used to be zlib compression, but has been swapped out with obfuscation instead
+    @staticmethod
+    def deobfuscate(server: Server, packet: bytes) -> bytes:
+        checksum, data = packet[0], bytearray(packet[1:])
+
+        data = Obfuscation.xor_every_other_byte(
+            Obfuscation.get_port_xor_key(server), data
+        )
+        data = bytes(Obfuscation.LOOKUP_TABLE[b] for b in packet)
+
+        if checksum != Obfuscation.calc_checksum(data):
+            logging.error("Checksum failed!")
+            raise Exception("Checksum fail")
+
+        return bytes(data)
+
+    @staticmethod
+    def obfuscate(server: Server, packet: bytes) -> bytes:
+        data = bytes(Obfuscation.LOOKUP_TABLE.index(b) for b in packet)
+        data = Obfuscation.xor_every_other_byte(
+            Obfuscation.get_port_xor_key(server), data
+        )
+
+        checksum = Obfuscation.calc_checksum(data)
+        return bytes([checksum]) + data
+
+    @staticmethod
+    def xor_every_other_byte(xor: int, packet: bytearray) -> bytearray:
+        for i in range(1, len(packet), 2):
+            packet[i] ^= xor
+        return packet
+
+    @staticmethod
+    def calc_checksum(packet: bytearray) -> int:
+        checksum = 0
+        for byte in packet:
+            checksum ^= byte & 0xAA
+        return checksum
+
+    @staticmethod
+    def get_port_xor_key(server: Server) -> int:
+        return (server.config.port ^ 0xCCCC) & 0xFF