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40 lines
1.3 KiB
Python
40 lines
1.3 KiB
Python
from hashlib import sha256
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from ..errors import CdnFileTamperedError
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class HashChecker:
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def __init__(self, cdn_file_hashes):
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self.cdn_file_hashes = cdn_file_hashes
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self.shaes = [sha256() for _ in range(len(cdn_file_hashes))]
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def check(self, offset, data):
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for cdn_hash, sha in zip(self.cdn_file_hashes, self.shaes):
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inter = self.intersect(
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cdn_hash.offset, cdn_hash.offset + cdn_hash.limit,
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offset, offset + len(data)
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)
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if inter:
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x1, x2 = inter[0] - offset, inter[1] - offset
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sha.update(data[x1:x2])
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elif offset > cdn_hash.offset:
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if cdn_hash.hash == sha.digest():
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self.cdn_file_hashes.remove(cdn_hash)
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self.shaes.remove(sha)
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else:
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raise CdnFileTamperedError()
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def finish_check(self):
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for cdn_hash, sha in zip(self.cdn_file_hashes, self.shaes):
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if cdn_hash.hash != sha.digest():
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raise CdnFileTamperedError()
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self.cdn_file_hashes.clear()
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self.shaes.clear()
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@staticmethod
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def intersect(x1, x2, z1, z2):
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if x1 > z1:
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return None if x1 > z2 else (x1, min(x2, z2))
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else:
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return (z1, min(x2, z2)) if x2 > z1 else None
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