39 lines
1.4 KiB
Python
39 lines
1.4 KiB
Python
import io
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from .matcher import SignatureMatcher, Match
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class Ambarella(SignatureMatcher):
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def __init__(self, file):
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self.name = "Ambarella Firmware Section"
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self.signature = b'\x90\xeb\x24\xa3'
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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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# walk back for the firmware section header
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start = match - 4*5
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header = io.BytesIO(self.file[start:start+228+4*6])
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crc = header.read(4)
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version_major = header.read(2)
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version_minor = header.read(2)
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filesize = header.read(4)
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memory = header.read(4)
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flag = header.read(4)
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magic = header.read(4)
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zeros = header.read()
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# for ambarella firmware, the magic is placed at offset 20
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# and after the magic, 228 bytes of \x00 must be placed
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# then crc value must match the CRC(<filesize> bytes after header)
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is_matched = magic == self.signature
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is_matched &= zeros == bytes(228)
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# is_matched &= crc == self.crc(self.file[start + 228+4*6:start + filesize + 228+4*6])
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if is_matched:
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# add the header offset to list of matches
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filesize = int.from_bytes(filesize, 'little')
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self.matches += [Match(start, 228 + 4*6 + filesize)]
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return len(self.matches) != 0
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