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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.
from __future__ import annotations
import os
from cryptography import exceptions, utils
from cryptography.hazmat.backends.openssl import aead
from cryptography.hazmat.backends.openssl.backend import backend
from cryptography.hazmat.bindings._rust import openssl as rust_openssl
__all__ = [
"ChaCha20Poly1305",
"AESCCM",
"AESGCM",
"AESGCMSIV",
"AESOCB3",
"AESSIV",
]
ChaCha20Poly1305 = rust_openssl.aead.ChaCha20Poly1305
AESSIV = rust_openssl.aead.AESSIV
AESOCB3 = rust_openssl.aead.AESOCB3
AESGCMSIV = rust_openssl.aead.AESGCMSIV
class AESCCM:
_MAX_SIZE = 2**31 - 1
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
if not backend.aead_cipher_supported(self):
raise exceptions.UnsupportedAlgorithm(
"AESCCM is not supported by this version of OpenSSL",
exceptions._Reasons.UNSUPPORTED_CIPHER,
)
@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: bytes | None,
) -> 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**31 - 1 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: bytes | None,
) -> 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) -> None:
# 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
) -> None:
utils._check_byteslike("nonce", nonce)
utils._check_byteslike("data", data)
utils._check_byteslike("associated_data", associated_data)
if not 7 <= len(nonce) <= 13:
raise ValueError("Nonce must be between 7 and 13 bytes")
class AESGCM:
_MAX_SIZE = 2**31 - 1
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: bytes | None,
) -> 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**31 - 1 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: bytes | None,
) -> 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_byteslike("data", data)
utils._check_byteslike("associated_data", associated_data)
if len(nonce) < 8 or len(nonce) > 128:
raise ValueError("Nonce must be between 8 and 128 bytes")