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cryptography
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aead.py
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# 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. import os import typing from cryptography import exceptions, utils from cryptography.hazmat.backends.openssl import aead from cryptography.hazmat.backends.openssl.backend import backend class ChaCha20Poly1305(object): _MAX_SIZE = 2 ** 32 def __init__(self, key: bytes): 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_byteslike("key", key) if len(key) != 32: raise ValueError("ChaCha20Poly1305 key must be 32 bytes.") self._key = key @classmethod def generate_key(cls) -> bytes: return os.urandom(32) def encrypt( self, nonce: bytes, data: bytes, associated_data: typing.Optional[bytes], ) -> bytes: 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) def decrypt( self, nonce: bytes, data: bytes, associated_data: typing.Optional[bytes], ) -> bytes: 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: bytes, data: bytes, associated_data: bytes, ) -> None: utils._check_byteslike("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") class AESCCM(object): _MAX_SIZE = 2 ** 32 def __init__(self, key: bytes, tag_length: int = 16): utils._check_byteslike("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 @classmethod def generate_key(cls, bit_length: int) -> bytes: 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) def encrypt( self, nonce: bytes, data: bytes, associated_data: typing.Optional[bytes], ) -> bytes: 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 ) def decrypt( self, nonce: bytes, data: bytes, associated_data: typing.Optional[bytes], ) -> bytes: 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: bytes, data_len: int): # 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("Data too long for nonce") def _check_params(self, nonce: bytes, data: bytes, associated_data: bytes): utils._check_byteslike("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") class AESGCM(object): _MAX_SIZE = 2 ** 32 def __init__(self, key: bytes): utils._check_byteslike("key", key) if len(key) not in (16, 24, 32): raise ValueError("AESGCM key must be 128, 192, or 256 bits.") self._key = key @classmethod def generate_key(cls, bit_length: int) -> bytes: 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) def encrypt( self, nonce: bytes, data: bytes, associated_data: typing.Optional[bytes], ) -> bytes: 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) def decrypt( self, nonce: bytes, data: bytes, associated_data: typing.Optional[bytes], ) -> bytes: 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: bytes, data: bytes, associated_data: bytes, ) -> None: utils._check_byteslike("nonce", nonce) utils._check_bytes("data", data) utils._check_bytes("associated_data", associated_data) if len(nonce) < 8 or len(nonce) > 128: raise ValueError("Nonce must be between 8 and 128 bytes")