302 lines
10 KiB
Python
302 lines
10 KiB
Python
import binascii
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import hashlib
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from typing import Optional
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from bemani.protocol.lz77 import Lz77
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from bemani.protocol.binary import BinaryEncoding
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from bemani.protocol.xml import XmlEncoding
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from bemani.protocol.node import Node
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class EAmuseException(Exception):
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"""
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An exception thrown when we encounter an error with E-Amusement encapsulation.
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"""
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class EAmuseProtocol:
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"""
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A wrapper object that encapsulates encoding/decoding the E-Amusement protocol by Konami.
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"""
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SHARED_SECRET = b'\x69\xD7\x46\x27\xD9\x85\xEE\x21\x87\x16\x15\x70\xD0\x8D\x93\xB1\x24\x55\x03\x5B\x6D\xF0\xD8\x20\x5D\xF5'
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XML = 1
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BINARY = 2
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SHIFT_JIS_LEGACY = "shift-jis-legacy"
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SHIFT_JIS = "shift-jis"
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EUC_JP = "euc-jp"
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UTF_8 = "utf-8"
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ASCII = "ascii"
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def __init__(self) -> None:
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"""
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Initialize the object.
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"""
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self.last_text_encoding: Optional[str] = None
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self.last_packet_encoding: Optional[int] = None
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def __rc4_crypt(self, data: bytes, key: bytes) -> bytes:
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"""
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Given a data blob and a key blob, perform RC4 encryption/decryption.
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Parameters:
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data - Binary string representing data to be encrypted/decrypted
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key - Binary string representing the key to use
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Returns:
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binary string representing the encrypted/decrypted data
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"""
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S = list(range(256))
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j = 0
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out = []
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# KSA Phase
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for i in range(256):
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j = (j + S[i] + key[i % len(key)]) & 0xFF
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S[i], S[j] = S[j], S[i]
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# PRGA Phase
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i = j = 0
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for char in data:
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i = (i + 1) & 0xFF
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j = (j + S[i]) & 0XFF
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S[i], S[j] = S[j], S[i]
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out.append(char ^ S[(S[i] + S[j]) & 0xFF])
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return bytes(out)
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def __decrypt(self, encryption_key: str, data: bytes) -> bytes:
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"""
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Given data and an optional encryption key, decrypt the data.
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Parameters:
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encryption_key - A string encryption key as returned from a HTTP request.
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Should be in the form 1-xxyyzzww-aabb. If it is None, this
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performs a null decrypt.
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data - Binary string representing data to transform.
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Returns:
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binary string representing transformed data
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"""
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if data is None:
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return None
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if encryption_key:
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# Key is concatenated with the shared secret above
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version, first, second = encryption_key.split('-')
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key = binascii.unhexlify((first + second).encode('ascii')) + EAmuseProtocol.SHARED_SECRET
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# Next, key is sent through MD5 to derive the real key
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m = hashlib.md5()
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m.update(key)
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key = m.digest()
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else:
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key = None
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if key:
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# This is an encrypted old-style packet
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return self.__rc4_crypt(data, key)
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# No encryption
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return data
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def __encrypt(self, encryption_key: str, data: bytes) -> bytes:
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"""
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Given data and an optional encryption key, encrypt the data.
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Parameters:
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encryption_key - A string encryption key as returned from a HTTP request.
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Should be in the form 1-xxyyzzww-aabb. If it is None, this
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performs a null decrypt.
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data - Binary string representing data to transform.
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Returns:
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binary string representing transformed data
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"""
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# RC4 is symmetric
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return self.__decrypt(encryption_key, data)
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def __decompress(self, compression: str, data: bytes) -> bytes:
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"""
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Given data and an optional compression scheme, decompress the data.
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Parameters:
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compression - A string specifying the compression used. Should
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be of the form 'l7zz' or 'none'. You can also pass in
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the python value None.
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data - Binary string representing data to transform.
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Returns:
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binary string representing transformed data
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"""
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if data is None:
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return None
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if compression:
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if compression is None or compression == 'none':
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# This isn't compressed
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return data
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elif compression == 'lz77':
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# This is a compressed new-style packet
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lz = Lz77()
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return lz.decompress(data)
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else:
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raise EAmuseException(f'Unknown compression {compression}')
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# No compression
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return data
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def __compress(self, compression: str, data: bytes) -> bytes:
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"""
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Given data and an optional compression scheme, compress the data.
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Parameters:
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compression - A string specifying the compression used. Should
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be of the form 'l7zz' or 'none'. The python value
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None will also be recognized as 'none'.
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data - Binary string representing data to transform.
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Returns:
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binary string representing transformed data
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"""
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if data is None:
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return None
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if compression:
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if compression is None or compression == 'none':
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# This isn't compressed
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return data
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elif compression == 'lz77':
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# This is a compressed new-style packet
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lz = Lz77()
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return lz.compress(data)
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else:
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raise EAmuseException(f'Unknown compression {compression}')
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# No compression
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return data
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def __decode(self, data: bytes) -> Node:
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"""
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Given data, decode the data into a Node tree.
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Parameters:
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data - Binary string representing data to decode.
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Returns:
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Node tree on success or None on failure.
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"""
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# Assume it's a binary page
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binary = BinaryEncoding()
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ret = binary.decode(data, skip_on_exceptions=True)
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if ret is not None:
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# We got a result, it was binary
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self.last_text_encoding = binary.encoding
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self.last_packet_encoding = EAmuseProtocol.BINARY
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return ret
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# Assume its XML
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xml = XmlEncoding()
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ret = xml.decode(data, skip_on_exceptions=True)
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if ret is not None:
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# We got a result, it was XML
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self.last_text_encoding = xml.encoding
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self.last_packet_encoding = EAmuseProtocol.XML
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return ret
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# Couldn't decode
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raise EAmuseException('Unknown packet encoding')
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def __encode(self, tree: Node, text_encoding: str, packet_encoding: int) -> bytes:
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"""
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Given a Node tree, encode the data into the given packet encoding.
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Parameters:
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tree - A Node object representing the root of the tree to encode.
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text_encoding - The text encoding for any strings that will be encoded.
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Should be EAmuseProtocol.SHIFT_JIS, EAmuseProtocol.EUC_JP or
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EAmuseProtocol.UTF8.
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packet_encoding - The encoding used for the packet. Should be EAmuseProtocol.XML
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or EAmuseProtocol.BINARY.
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Returns:
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A string blob representing the encoded packet.
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"""
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if packet_encoding == EAmuseProtocol.BINARY:
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# It's binary, encode it
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binary = BinaryEncoding()
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return binary.encode(tree, encoding=text_encoding)
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elif packet_encoding == EAmuseProtocol.XML:
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# It's XML, encode it
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xml = XmlEncoding()
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return xml.encode(tree, encoding=text_encoding)
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else:
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raise EAmuseException(f"Invalid packet encoding {packet_encoding}")
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def decode(self, compression: Optional[str], encryption: Optional[str], data: bytes) -> Node:
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"""
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Given a request with optional compression and encryption set, decrypt,
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decompress and decode the data, returning a parsed tree.
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Parameters:
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compression - A string specifying the compression type, should be 'lz77' or 'none'.
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The python value None can also be passed in.
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encryption - A string specifying the encryption key, or None if no encryption.
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data - A binary string of data to parse.
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Returns:
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A Node tree structure representing the parsed request, or None on failure.
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"""
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data = self.__decrypt(encryption, data)
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data = self.__decompress(compression, data)
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return self.__decode(data)
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def encode(
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self,
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compression: Optional[str],
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encryption: Optional[str],
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tree: Node,
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text_encoding: Optional[str]=None,
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packet_encoding: Optional[int]=None,
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) -> bytes:
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"""
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Given a response with optional compression and encryption set, encode, compress
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and encrypt the data, returning a binary blob suitable for forwarding on a network.
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Parameters:
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compression - A string specifying the compression type, should be 'lz77' or 'none'.
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The python value None can also be passed in.
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encryption - A string specifying the encryption key, or None if no encryption.
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data - A binary string of data to parse.
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text_encoding - A text encoding to use. If not provided, uses the text encoding of the
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last decoded packet. See __encode for values.
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packet_encpding - A packet encoding to use. If not provided, uses the packet encoding
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of the last decoded packet. See __encode for values.
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Returns:
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A blob of data representing the encoded packet.
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"""
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# Either auto-set response based on request, or explicitly override in parameters
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if text_encoding is None:
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text_encoding = self.last_text_encoding
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if text_encoding is None:
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raise EAmuseException("Unknown text encoding")
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if packet_encoding is None:
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packet_encoding = self.last_packet_encoding
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if packet_encoding is None:
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raise EAmuseException("Unknown packet encoding")
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# Clear last packet since we sent a response
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self.last_text_encoding = None
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self.last_packet_encoding = None
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data = self.__encode(tree, text_encoding, packet_encoding)
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data = self.__compress(compression, data)
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return self.__encrypt(encryption, data)
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