本文整理汇总了Python中cryptography.exceptions方法的典型用法代码示例。如果您正苦于以下问题：Python cryptography.exceptions方法的具体用法？Python cryptography.exceptions怎么用？Python cryptography.exceptions使用的例子？那么恭喜您, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在类cryptography的用法示例。
在下文中一共展示了cryptography.exceptions方法的1个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的Python代码示例。
示例1: _decrypt
# 需要导入模块: import cryptography [as 别名]
# 或者: from cryptography import exceptions [as 别名]
def _decrypt(file_contents, password):
"""
The corresponding decryption routine for _encrypt().
'securesystemslib.exceptions.CryptoError' raised if the decryption fails.
"""
# Extract the salt, iterations, hmac, initialization vector, and ciphertext
# from 'file_contents'. These five values are delimited by
# '_ENCRYPTION_DELIMITER'. This delimiter is arbitrarily chosen and should
# not occur in the hexadecimal representations of the fields it is
# separating. Raise 'securesystemslib.exceptions.CryptoError', if
# 'file_contents' does not contains the expected data layout.
try:
salt, iterations, hmac, iv, ciphertext = \
file_contents.split(_ENCRYPTION_DELIMITER)
except ValueError:
raise securesystemslib.exceptions.CryptoError('Invalid encrypted file.')
# Ensure we have the expected raw data for the delimited cryptographic data.
salt = binascii.unhexlify(salt.encode('utf-8'))
iterations = int(iterations)
iv = binascii.unhexlify(iv.encode('utf-8'))
ciphertext = binascii.unhexlify(ciphertext.encode('utf-8'))
# Generate derived key from 'password'. The salt and iterations are
# specified so that the expected derived key is regenerated correctly.
# Discard the old "salt" and "iterations" values, as we only need the old
# derived key.
junk_old_salt, junk_old_iterations, symmetric_key = \
_generate_derived_key(password, salt, iterations)
# Verify the hmac to ensure the ciphertext is valid and has not been altered.
# See the encryption routine for why we use the encrypt-then-MAC approach.
# The decryption routine may verify a ciphertext without having to perform
# a decryption operation.
generated_hmac_object = \
cryptography.hazmat.primitives.hmac.HMAC(symmetric_key, hashes.SHA256(),
backend=default_backend())
generated_hmac_object.update(ciphertext)
generated_hmac = binascii.hexlify(generated_hmac_object.finalize())
if not securesystemslib.util.digests_are_equal(generated_hmac.decode(), hmac):
raise securesystemslib.exceptions.CryptoError('Decryption failed.')
# Construct a Cipher object, with the key and iv.
decryptor = Cipher(algorithms.AES(symmetric_key), modes.CTR(iv),
backend=default_backend()).decryptor()
# Decryption gets us the authenticated plaintext.
plaintext = decryptor.update(ciphertext) + decryptor.finalize()
return plaintext