# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.
from __future__ import absolute_import, division, print_function
import os
from cryptography import exceptions, utils
from cryptography.hazmat.backends.openssl import aead
from cryptography.hazmat.backends.openssl.backend import backend
[docs]class ChaCha20Poly1305(object):
_MAX_SIZE = 2 ** 32
def __init__(self, key):
if not backend.aead_cipher_supported(self):
raise exceptions.UnsupportedAlgorithm(
"ChaCha20Poly1305 is not supported by this version of OpenSSL",
exceptions._Reasons.UNSUPPORTED_CIPHER
)
utils._check_bytes("key", key)
if len(key) != 32:
raise ValueError("ChaCha20Poly1305 key must be 32 bytes.")
self._key = key
[docs] @classmethod
def generate_key(cls):
return os.urandom(32)
[docs] def encrypt(self, nonce, data, associated_data):
if associated_data is None:
associated_data = b""
if len(data) > self._MAX_SIZE or len(associated_data) > self._MAX_SIZE:
# This is OverflowError to match what cffi would raise
raise OverflowError(
"Data or associated data too long. Max 2**32 bytes"
)
self._check_params(nonce, data, associated_data)
return aead._encrypt(
backend, self, nonce, data, associated_data, 16
)
[docs] def decrypt(self, nonce, data, associated_data):
if associated_data is None:
associated_data = b""
self._check_params(nonce, data, associated_data)
return aead._decrypt(
backend, self, nonce, data, associated_data, 16
)
def _check_params(self, nonce, data, associated_data):
utils._check_bytes("nonce", nonce)
utils._check_bytes("data", data)
utils._check_bytes("associated_data", associated_data)
if len(nonce) != 12:
raise ValueError("Nonce must be 12 bytes")
[docs]class AESCCM(object):
_MAX_SIZE = 2 ** 32
def __init__(self, key, tag_length=16):
utils._check_bytes("key", key)
if len(key) not in (16, 24, 32):
raise ValueError("AESCCM key must be 128, 192, or 256 bits.")
self._key = key
if not isinstance(tag_length, int):
raise TypeError("tag_length must be an integer")
if tag_length not in (4, 6, 8, 10, 12, 14, 16):
raise ValueError("Invalid tag_length")
self._tag_length = tag_length
if not backend.aead_cipher_supported(self):
raise exceptions.UnsupportedAlgorithm(
"AESCCM is not supported by this version of OpenSSL",
exceptions._Reasons.UNSUPPORTED_CIPHER
)
[docs] @classmethod
def generate_key(cls, bit_length):
if not isinstance(bit_length, int):
raise TypeError("bit_length must be an integer")
if bit_length not in (128, 192, 256):
raise ValueError("bit_length must be 128, 192, or 256")
return os.urandom(bit_length // 8)
[docs] def encrypt(self, nonce, data, associated_data):
if associated_data is None:
associated_data = b""
if len(data) > self._MAX_SIZE or len(associated_data) > self._MAX_SIZE:
# This is OverflowError to match what cffi would raise
raise OverflowError(
"Data or associated data too long. Max 2**32 bytes"
)
self._check_params(nonce, data, associated_data)
self._validate_lengths(nonce, len(data))
return aead._encrypt(
backend, self, nonce, data, associated_data, self._tag_length
)
[docs] def decrypt(self, nonce, data, associated_data):
if associated_data is None:
associated_data = b""
self._check_params(nonce, data, associated_data)
return aead._decrypt(
backend, self, nonce, data, associated_data, self._tag_length
)
def _validate_lengths(self, nonce, data_len):
# For information about computing this, see
# https://tools.ietf.org/html/rfc3610#section-2.1
l_val = 15 - len(nonce)
if 2 ** (8 * l_val) < data_len:
raise ValueError("Nonce too long for data")
def _check_params(self, nonce, data, associated_data):
utils._check_bytes("nonce", nonce)
utils._check_bytes("data", data)
utils._check_bytes("associated_data", associated_data)
if not 7 <= len(nonce) <= 13:
raise ValueError("Nonce must be between 7 and 13 bytes")
[docs]class AESGCM(object):
_MAX_SIZE = 2 ** 32
def __init__(self, key):
utils._check_bytes("key", key)
if len(key) not in (16, 24, 32):
raise ValueError("AESGCM key must be 128, 192, or 256 bits.")
self._key = key
[docs] @classmethod
def generate_key(cls, bit_length):
if not isinstance(bit_length, int):
raise TypeError("bit_length must be an integer")
if bit_length not in (128, 192, 256):
raise ValueError("bit_length must be 128, 192, or 256")
return os.urandom(bit_length // 8)
[docs] def encrypt(self, nonce, data, associated_data):
if associated_data is None:
associated_data = b""
if len(data) > self._MAX_SIZE or len(associated_data) > self._MAX_SIZE:
# This is OverflowError to match what cffi would raise
raise OverflowError(
"Data or associated data too long. Max 2**32 bytes"
)
self._check_params(nonce, data, associated_data)
return aead._encrypt(
backend, self, nonce, data, associated_data, 16
)
[docs] def decrypt(self, nonce, data, associated_data):
if associated_data is None:
associated_data = b""
self._check_params(nonce, data, associated_data)
return aead._decrypt(
backend, self, nonce, data, associated_data, 16
)
def _check_params(self, nonce, data, associated_data):
utils._check_bytes("nonce", nonce)
utils._check_bytes("data", data)
utils._check_bytes("associated_data", associated_data)
if len(nonce) == 0:
raise ValueError("Nonce must be at least 1 byte")