129 lines
4.2 KiB
Python
129 lines
4.2 KiB
Python
import logging
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from typing import Union, Tuple, Dict
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from . import abstract
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class TorrentParser(abstract.AbstractParser):
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mimetypes = {'application/x-bittorrent', }
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allowlist = {b'announce', b'announce-list', b'info'}
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def __init__(self, filename):
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super().__init__(filename)
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with open(self.filename, 'rb') as f:
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self.dict_repr = _BencodeHandler().bdecode(f.read())
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if self.dict_repr is None:
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raise ValueError
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def get_meta(self) -> Dict[str, Union[str, dict]]:
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metadata = {}
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for key, value in self.dict_repr.items():
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if key not in self.allowlist:
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metadata[key.decode('utf-8')] = value
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return metadata
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def remove_all(self) -> bool:
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cleaned = dict()
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for key, value in self.dict_repr.items():
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if key in self.allowlist:
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cleaned[key] = value
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with open(self.output_filename, 'wb') as f:
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f.write(_BencodeHandler().bencode(cleaned))
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self.dict_repr = cleaned # since we're stateful
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return True
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class _BencodeHandler():
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"""
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Since bencode isn't that hard to parse,
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MAT2 comes with its own parser, based on the spec
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https://wiki.theory.org/index.php/BitTorrentSpecification#Bencoding
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"""
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def __init__(self):
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self.__decode_func = {
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ord('d'): self.__decode_dict,
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ord('i'): self.__decode_int,
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ord('l'): self.__decode_list,
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}
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for i in range(0, 10):
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self.__decode_func[ord(str(i))] = self.__decode_string
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self.__encode_func = {
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bytes: self.__encode_string,
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dict: self.__encode_dict,
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int: self.__encode_int,
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list: self.__encode_list,
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}
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@staticmethod
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def __decode_int(s: bytes) -> Tuple[int, bytes]:
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s = s[1:]
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next_idx = s.index(b'e')
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if s.startswith(b'-0'):
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raise ValueError # negative zero doesn't exist
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elif s.startswith(b'0') and next_idx != 1:
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raise ValueError # no leading zero except for zero itself
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return int(s[:next_idx]), s[next_idx+1:]
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@staticmethod
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def __decode_string(s: bytes) -> Tuple[bytes, bytes]:
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colon = s.index(b':')
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# FIXME Python3 is broken here, the call to `ord` shouldn't be needed,
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# but apparently it is. This is utterly idiotic.
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if (s[0] == ord('0') or s[0] == '0') and colon != 1:
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raise ValueError
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str_len = int(s[:colon])
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s = s[1:]
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return s[colon:colon+str_len], s[colon+str_len:]
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def __decode_list(self, s: bytes) -> Tuple[list, bytes]:
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ret = list()
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s = s[1:] # skip leading `l`
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while s[0] != ord('e'):
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value, s = self.__decode_func[s[0]](s)
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ret.append(value)
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return ret, s[1:]
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def __decode_dict(self, s: bytes) -> Tuple[dict, bytes]:
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ret = dict()
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s = s[1:] # skip leading `d`
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while s[0] != ord(b'e'):
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key, s = self.__decode_string(s)
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ret[key], s = self.__decode_func[s[0]](s)
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return ret, s[1:]
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@staticmethod
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def __encode_int(x: bytes) -> bytes:
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return b'i' + bytes(str(x), 'utf-8') + b'e'
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@staticmethod
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def __encode_string(x: bytes) -> bytes:
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return bytes((str(len(x))), 'utf-8') + b':' + x
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def __encode_list(self, x: str) -> bytes:
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ret = b''
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for i in x:
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ret += self.__encode_func[type(i)](i)
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return b'l' + ret + b'e'
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def __encode_dict(self, x: dict) -> bytes:
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ret = b''
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for key, value in sorted(x.items()):
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ret += self.__encode_func[type(key)](key)
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ret += self.__encode_func[type(value)](value)
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return b'd' + ret + b'e'
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def bencode(self, s: Union[dict, list, bytes, int]) -> bytes:
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return self.__encode_func[type(s)](s)
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def bdecode(self, s: bytes) -> Union[dict, None]:
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try:
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ret, trail = self.__decode_func[s[0]](s)
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except (IndexError, KeyError, ValueError) as e:
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logging.warning("Not a valid bencoded string: %s", e)
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return None
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if trail != b'':
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logging.warning("Invalid bencoded value (data after valid prefix)")
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return None
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return ret
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