56 lines
1.4 KiB
Python
56 lines
1.4 KiB
Python
import base64
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import hmac
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import os
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from .crypto_backend import (
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AES_BLOCK_BYTES,
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aes_cfb8_encrypt,
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aes_cfb8_decrypt,
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aes_cfb128_encrypt,
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aes_cfb128_decrypt,
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)
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KEY_SIZE_BYTES = 32
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SHA256_HMAC_BYTES = 32
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def _xor_bytes(a, b):
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assert(len(a) == len(b))
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return bytes([ax ^ bx for ax, bx in zip(a, b)])
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def _fold_key(buf):
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assert(len(buf) == 32)
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return _xor_bytes(buf[:16], buf[16:])
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def generate_key():
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return os.urandom(KEY_SIZE_BYTES)
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def sha256_hmac(buf, key):
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return hmac.new(key, buf, digestmod="sha256").digest()
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def aes_cfb8_wrap(data, key):
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iv = os.urandom(AES_BLOCK_BYTES)
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ct = aes_cfb8_encrypt(data, key, iv)
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buf = iv + ct
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return sha256_hmac(buf, key) + buf
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def aes_cfb8_unwrap(buf, key):
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mac, buf = buf[:SHA256_HMAC_BYTES], buf[SHA256_HMAC_BYTES:]
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if sha256_hmac(buf, key) != mac:
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raise IOError("MAC verification failed")
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iv, ct = buf[:AES_BLOCK_BYTES], buf[AES_BLOCK_BYTES:]
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return aes_cfb8_decrypt(ct, key, iv)
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def aes_cfb128_wrap(data, key):
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iv = os.urandom(AES_BLOCK_BYTES)
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ct = aes_cfb128_encrypt(data, key, iv)
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buf = iv + ct
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return sha256_hmac(buf, key) + buf
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def aes_cfb128_unwrap(buf, key):
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mac, buf = buf[:SHA256_HMAC_BYTES], buf[SHA256_HMAC_BYTES:]
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if sha256_hmac(buf, key) != mac:
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raise IOError("MAC verification failed")
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iv, ct = buf[:AES_BLOCK_BYTES], buf[AES_BLOCK_BYTES:]
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return aes_cfb128_decrypt(ct, key, iv)
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