forked from Archive/PX4-Autopilot
63 lines
2.2 KiB
Python
Executable File
63 lines
2.2 KiB
Python
Executable File
#!/usr/bin/env python3
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from Crypto.PublicKey import RSA
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from Crypto.Cipher import PKCS1_OAEP
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from Crypto.Cipher import ChaCha20
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from Crypto.Hash import SHA256
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import binascii
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import argparse
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#from pathlib import Path
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import sys
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if __name__ == "__main__":
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parser = argparse.ArgumentParser(description="""CLI tool to decrypt an ulog file\n""")
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parser.add_argument("ulog_file", help=".ulog file", nargs='?', default=None)
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parser.add_argument("ulog_key", help=".ulogk, encrypted key", nargs='?', default=None)
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parser.add_argument("rsa_key", help=".pem format key for decrypting the ulog key", nargs='?', default=None)
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args = parser.parse_args()
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# Only generate a key pair, don't sign
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if not args.ulog_file or not args.ulog_key or not args.rsa_key:
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print('Need all arguments, the encrypted ulog file, the key and the key decryption key')
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sys.exit(1);
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# Read the private RSA key to decrypt the cahcha key
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with open(args.rsa_key, 'rb') as f:
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r = RSA.importKey(f.read(), passphrase='')
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# Read the encrypted xchacha key and the nonce
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with open(args.ulog_key, 'rb') as f:
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ulog_key_header = f.read(22)
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# Parse the header
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try:
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# magic
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if not ulog_key_header.startswith(bytearray("ULogKey".encode())):
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raise Exception()
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# version
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if ulog_key_header[7] != 1:
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raise Exception()
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# expected key exchange algorithm (RSA_OAEP)
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if ulog_key_header[16] != 4:
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raise Exception()
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key_size = ulog_key_header[19] << 8 | ulog_key_header[18];
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nonce_size = ulog_key_header[21] << 8 | ulog_key_header[20];
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ulog_key_cipher = f.read(key_size)
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nonce = f.read(nonce_size)
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except:
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print("Keyfile format error")
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sys.exit(1);
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# Decrypt the xchacha key
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cipher_rsa = PKCS1_OAEP.new(r,SHA256)
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ulog_key = cipher_rsa.decrypt(ulog_key_cipher)
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#print(binascii.hexlify(ulog_key))
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# Read and decrypt the .ulgc
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cipher = ChaCha20.new(key=ulog_key, nonce=nonce)
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with open(args.ulog_file, 'rb') as f:
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with open(args.ulog_file.rstrip(args.ulog_file[-1]), 'wb') as out:
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out.write(cipher.decrypt(f.read()))
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