Implemented compressor

sampy/server/__init__.py

@@ -2,8 +2,10 @@ import socket
 import asyncio
 from select import select # This is straight up magic
 
-from .struct.server import ServerConfig
-from .client import Client
+from ..struct.server import ServerConfig
+from ..client import Client
+
+from .compression import Compressor
 
 import logging
 logger = logging.getLogger(__name__)
@@ -13,6 +15,8 @@ class Server:
         self.config = config
         self.clients = {}
         self.rcon_clients = {}
+
+        self.compressor = Compressor(self.config)
     
     async def create_socket(self):
         self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)

sampy/server/compression.py

@@ -0,0 +1,48 @@
+from ..shared import glob
+from ..struct.server import ServerConfig
+
+import logging
+logger = logging.getLogger(__name__)
+
+# Found @ addr 0x004C88E0
+LOOKUP_TABLE = b"\xb4b\x07\xe5\x9d\xafc\xdd\xe3\xd0\xcc\xfe\xdc\xdbk.j@\xabG\xc9\xd1S\xd5 \x91\xa5\x0eJ\xdf\x18\x89\xfdo%\x12\xb7\x13w\x00e6mI\xecW*\xa9\x11_\xfax\x95\xa4\xbd\x1e\xd9yD\xcd\xde\x81\xeb\t>\xf6\xee\xda\x7f\xa3\x1a\xa7-\xa6\xad\xc1F\x93\xd2\x1b\x9c\xaa\xd7NKML\xf3\xb84\xc0\xca\x88\xf4\x94\xcb\x0490\x82\xd6s\xb0\xbf\"\x01AnH,\xa8u\xb1\n\xae\x9f\'\x80\x10\xce\xf0)(\x85\r\x05\xf75\xbb\xbc\x15\x06\xf5`q\x03\x1f\xeaZ3\x92\x8d\xe7\x90[\xe9\xcf\x9e\xd3]\xed1\x1c\x0bR\x16Q\x0f\x86\xc5h\x9b!\x0c\x8bB\x87\xffO\xbe\xc8\xe8\xc7\xd4z\xe0U/\x8a\x8e\xba\x987\xe4\xb28\xa1\xb62\x83:{\x84<a\xfb\x8c\x14=C;\x1d\xc3\xa2\x96\xb3\xf8\xc4\xf2&+\xd8|\xfc#$f\xefidPTY\xf1\xa0t\xac\xc6}\xb5\xe6\xe2\xc2~g\x17^\xe1\xb9?lp\x08\x99EVv\xf9\x9a\x97\x19r\\\x02\x8fX"
+
+class Compressor:
+    def __init__(self, config: ServerConfig):
+        self.config = config
+
+    def decompress(self, bytestream: bytes) -> bytes:
+        """Decompress client packet.
+        This is actually a deobfuscation as there is no compression involved anymore
+        as zlib was removed and just swapped with this implementation after the leak.
+
+        Arguments:
+            bytestream {bytes} -- Bytes sent by client
+        """
+        checksum, data = bytestream[0], bytestream[1:]
+
+        data = self.xor_every_other_byte(self.get_port_xor_key(), data)
+        data = self.run_though_lookup_table(data)
+
+        if checksum != self.calc_checksum(data):
+            logger.error("Checksum failed!")
+            raise Exception("Checksum fail")
+
+        return data
+
+    def xor_every_other_byte(self, xor: int, bytestream: bytes) -> bytes:
+        for i in range(1, len(bytestream), 2):
+            bytestream[i] ^= xor
+        return bytestream
+
+    def run_though_lookup_table(self, bytestream: bytes) -> bytes:
+        return bytes(LOOKUP_TABLE[b] for b in bytestream)
+    
+    def calc_checksum(self, bytestream: bytes) -> int:
+        checksum = 0
+        for byte in bytestream:
+            checksum ^= byte & 0xAA
+        return checksum
+
+    def get_port_xor_key(self) -> int:
+        return (self.config.port ^ 0xCCCC) & 0xFF