58 lines
1.4 KiB
Python
Executable File
58 lines
1.4 KiB
Python
Executable File
#!/usr/bin/env python3
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import hashlib
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from Crypto.Cipher import AES
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from Crypto.Util import Padding
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from Crypto.Hash import HMAC, SHA256
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import sys
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from getpass import getpass
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IV_LENGTH = 16
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NONCE_LENGTH = 16
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MAC_LENGTH = 16
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FORMAT_STRING = 'window.Signal.Backup.exportToDirectory(\'{0}\', {{\'key\':new Uint8Array({1})}});'
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def read_file(path):
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with open(path, 'rb') as fh:
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return fh.read()
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def decrypt(cipherkey, iv, ciphertext):
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cipher = AES.new(cipherkey, AES.MODE_CBC, iv)
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return Padding.unpad(cipher.decrypt(ciphertext), AES.block_size)
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def generate_cipherkey(key, nonce):
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h = HMAC.new(key, digestmod=SHA256)
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h.update(nonce)
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return h.digest()
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def generate_key(password):
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m = hashlib.sha256()
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m.update(password)
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return m.digest()
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def main():
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password = getpass()
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key = generate_key(password.encode('utf-8'))
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# generate string to be pasted in Signal-Desktop
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if len(sys.argv) == 1:
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print(FORMAT_STRING.format('/tmp/signal/', [elem for elem in key]))
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return
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# read encrypted file from disk
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data = read_file(sys.argv[1])
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# crypto foo
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iv = bytearray(IV_LENGTH) # IV is just 16 zeros
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nonce = data[:NONCE_LENGTH]
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ciphertext = data[NONCE_LENGTH:-MAC_LENGTH]
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cipherkey = generate_cipherkey(key, nonce)
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# save decrypted file to 'decrypted'
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with open('decrypted', 'wb') as fh:
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fh.write(decrypt(cipherkey, iv, ciphertext))
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if __name__ == '__main__':
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main()
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