45 lines
1.6 KiB
Python
45 lines
1.6 KiB
Python
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import io
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from .matcher import SignatureMatcher, Match
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class Zip(SignatureMatcher):
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"""
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Zip files are read from the bottom
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The signature PK is the local file header
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https://medium.com/@felixstridsberg/the-zip-file-format-6c8a160d1c34
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"""
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def __init__(self, file):
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self.name = "Zip"
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self.signature = b'PK\x03\x04'
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super().__init__(file)
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def is_valid(self):
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for match in self.search():
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start = match
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header = io.BytesIO(self.file[start:start+4*4 + 2*7])
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magic = header.read(4)
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min_version = header.read(2)
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bitflag = header.read(2)
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compression_method = header.read(2)
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last_modification_time = header.read(2)
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last_modification_data = header.read(2)
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crc = header.read(4)
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compressed_size = header.read(4)
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uncompressed_size = header.read(4)
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file_name_length = header.read(2)
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extra_field_length = header.read(2)
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file_name_length = int.from_bytes(file_name_length, 'little')
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extra_field_length = int.from_bytes(extra_field_length, 'little')
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compressed_size = int.from_bytes(compressed_size, 'little')
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header_size = 4*4 + 2*7
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data = {
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'name': self.file[start+header_size:start+header_size+file_name_length]
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}
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size = 4*4 + 2*7 + file_name_length + extra_field_length + compressed_size
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self.matches += [Match(start, size, data)]
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return len(self.matches) != 0
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