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"""This module provides methods for symmetric cryptography.
The default symmetric cryptography method used is Fernet by the cryptography
library. Reference: https://cryptography.io/en/latest/fernet/
"""
import base64 as _base64
import os as _os
import logging
from warnings import warn as _warn
import cryptography.fernet as _fernet
import cryptography.hazmat.backends as _backends
import cryptography.hazmat.primitives.ciphers as _ciphers
from .errors import SymmetricCryptographyError
logger = logging.getLogger(__name__)
class Fernet(object):
"""The default symmetric cryptography method."""
@staticmethod
def generate_key():
"""Return a key suitable for use by this method.
:return: byte data representing the encyption/decryption key
"""
key = _fernet.Fernet.generate_key()
return key
def __init__(self, key=None):
"""Initialize this method by optionally providing a key.
:param key: byte data representing the encyption/decryption key
"""
if key:
fernet_key_error = SymmetricCryptographyError(
"Fernet key must be 32 url-safe base64-encoded bytes."
)
try:
raw_key = _base64.b64decode(key)
except Exception as e:
raise fernet_key_error from e
else:
if len(raw_key) != 32:
raise fernet_key_error
else:
key = self.__class__.generate_key()
self._symmetric = _fernet.Fernet(key)
def encrypt(self, plaintext, *args, **kwargs):
"""Encrypt the given plaintext.
:param plaintext: byte data representing the plaintext
:return: byte data representing the ciphertext
"""
if args or kwargs:
_deprecation_msg = (
"The '.encrypt' method does not take into account any arguements, "
"other than the 'ciphertext' param. "
"Remove any other arguements. "
"In the next version, this method will not allow them."
)
logger.warning(_deprecation_msg)
_warn(_deprecation_msg, DeprecationWarning)
ciphertext = self._symmetric.encrypt(plaintext)
return ciphertext
def decrypt(self, ciphertext, *args, **kwargs):
"""Decrypt the given ciphertext.
:param ciphertext: byte data representing the ciphertext
:return: byte data representing the plaintext
"""
if args or kwargs:
_deprecation_msg = (
"The '.decrypt' method does not take into account any arguements, "
"other than the 'ciphertext' param. "
"Remove any other arguements. "
"In the next version, this method will not allow them."
)
logger.warning(_deprecation_msg)
_warn(_deprecation_msg, DeprecationWarning)
plaintext = self._symmetric.decrypt(ciphertext)
return plaintext
def build_cipher(self, *args, **kwargs):
_deprecation_msg = (
"The 'Fernet' class does not need a build_cipher method."
"Remove any calls to this method. "
"In the next version, this method will be removed."
)
logger.warning(_deprecation_msg)
_warn(_deprecation_msg, DeprecationWarning)
class AESCipher(object):
"""[deprecated] Symmetric cryptography method using AES.
The default parameter set is AES 128bit in CBC mode.
"""
POSTFIX_MODE = {
'cbc': _ciphers.modes.CBC,
'cfb': _ciphers.modes.CFB,
}
AES_BLOCK_SIZE = int(_ciphers.algorithms.AES.block_size / 8)
@classmethod
def _deprecation_notice(cls):
"""Warn about deprecation of this class."""
_deprecation_msg = (
'{name} {type} is deprecated. '
'It will be removed in the next version. '
'Use saml2.cryptography.symmetric.Default '
'or saml2.cryptography.symmetric.Fernet '
'instead.'
).format(name=cls.__name__, type=type(cls).__name__)
logger.warning(_deprecation_msg)
_warn(_deprecation_msg, DeprecationWarning)
def __init__(self, key):
"""
:param key: The encryption key
:return: AESCipher instance
"""
self.__class__._deprecation_notice()
self.key = key
def build_cipher(self, alg='aes_128_cbc'):
"""
:param alg: cipher algorithm
:return: A Cipher instance
"""
self.__class__._deprecation_notice()
typ, bits, cmode = alg.lower().split('_')
bits = int(bits)
iv = _os.urandom(self.AES_BLOCK_SIZE)
if len(iv) != self.AES_BLOCK_SIZE:
raise Exception('Wrong iv size: {}'.format(len(iv)))
if bits not in _ciphers.algorithms.AES.key_sizes:
raise Exception('Unsupported key length: {}'.format(bits))
if len(self.key) != bits / 8:
raise Exception('Wrong Key length: {}'.format(len(self.key)))
try:
mode = self.POSTFIX_MODE[cmode]
except KeyError:
raise Exception('Unsupported chaining mode: {}'.format(cmode))
cipher = _ciphers.Cipher(
_ciphers.algorithms.AES(self.key),
mode(iv),
backend=_backends.default_backend())
return cipher, iv
def encrypt(self, msg, alg='aes_128_cbc', padding='PKCS#7', b64enc=True,
block_size=AES_BLOCK_SIZE):
"""
:param key: The encryption key
:param msg: Message to be encrypted
:param padding: Which padding that should be used
:param b64enc: Whether the result should be base64encoded
:param block_size: If PKCS#7 padding which block size to use
:return: The encrypted message
"""
self.__class__._deprecation_notice()
if padding == 'PKCS#7':
_block_size = block_size
elif padding == 'PKCS#5':
_block_size = 8
else:
_block_size = 0
if _block_size:
plen = _block_size - (len(msg) % _block_size)
c = chr(plen).encode()
msg += c * plen
cipher, iv = self.build_cipher(alg)
encryptor = cipher.encryptor()
cmsg = iv + encryptor.update(msg) + encryptor.finalize()
if b64enc:
enc_msg = _base64.b64encode(cmsg)
else:
enc_msg = cmsg
return enc_msg
def decrypt(self, msg, alg='aes_128_cbc', padding='PKCS#7', b64dec=True):
"""
:param key: The encryption key
:param msg: Base64 encoded message to be decrypted
:return: The decrypted message
"""
self.__class__._deprecation_notice()
data = _base64.b64decode(msg) if b64dec else msg
cipher, iv = self.build_cipher(alg=alg)
decryptor = cipher.decryptor()
res = decryptor.update(data)[self.AES_BLOCK_SIZE:]
res += decryptor.finalize()
if padding in ['PKCS#5', 'PKCS#7']:
idx = bytearray(res)[-1]
res = res[:-idx]
return res
class Default(Fernet):
"""Default class is saml2.cryptography.symmetric.Fernet"""
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