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https://github.com/aljazceru/python-teos.git
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babb746dbd
Moves cryptographer to common. Also adds constants and defines the leghtn of the locator to avoid hardcoding it in almost every file
52 lines
1.6 KiB
Python
52 lines
1.6 KiB
Python
from hashlib import sha256
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from binascii import unhexlify, hexlify
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from cryptography.exceptions import InvalidTag
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from cryptography.hazmat.primitives.ciphers.aead import ChaCha20Poly1305
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from pisa.logger import Logger
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logger = Logger("Cryptographer")
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# FIXME: Cryptographer is assuming AES-128-GCM and SHA256 since they are the only pair accepted by the encrypted blob
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# and the only pair programmed so far.
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class Cryptographer:
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@staticmethod
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# ToDo: #20-test-tx-decrypting-edge-cases
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def decrypt(encrypted_blob, key, rtype="hex"):
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if rtype not in ["hex", "bytes"]:
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raise ValueError("Wrong return type. Return type must be 'hex' or 'bytes'")
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if len(encrypted_blob.data) % 2:
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logger.info(
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"Incorrect (Odd-length) value to be decrypted.", encrypted_blob=encrypted_blob.data, dispute_txid=key
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)
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return None
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# sk is the H(txid) (32-byte) and nonce is set to 0 (12-byte)
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sk = sha256(unhexlify(key)).digest()
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nonce = bytearray(12)
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logger.info(
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"Creating new blob.",
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sk=hexlify(sk).decode(),
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nonce=hexlify(nonce).decode(),
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encrypted_blob=encrypted_blob.data,
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)
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# Decrypt
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cipher = ChaCha20Poly1305(sk)
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data = unhexlify(encrypted_blob.data.encode())
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try:
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blob = cipher.decrypt(nonce=nonce, data=data, associated_data=None)
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# Change the blob encoding to hex depending on the rtype (default)
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if rtype == "hex":
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blob = hexlify(blob).decode("utf8")
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except InvalidTag:
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blob = None
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return blob
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