Created
December 23, 2021 00:05
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Decrypt firmware images for (some) EnGenius devices
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| #!/usr/bin/env python3 | |
| import sys | |
| key = b'\xac\x78\x3c\x9e\xcf\x67\xb3\x59' | |
| filename = sys.argv[1] | |
| def decrypter(reference): | |
| n = len(key) | |
| def decrypt(value, offset): | |
| nonlocal n, reference | |
| return value ^ key[(offset-reference)%n] | |
| return decrypt | |
| with open(filename, 'rb') as f: | |
| s = bytearray(f.read()) | |
| n = s[0x87] | |
| d = n + 0x88 | |
| end = len(s) | |
| decrypt = decrypter(s.find(key)) | |
| sys.stdout.buffer.write(bytes(s[0:d])) | |
| while d < end: | |
| stop = min(d + 4096, end) | |
| for offset in range(d, stop): | |
| s[offset] = decrypt(s[offset], offset) | |
| sys.stdout.buffer.write(bytes(s[d:stop])) | |
| d = stop |
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