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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 absolute_import, division, print_function
import binascii
import os
import struct
import pytest
from cryptography.hazmat.backends.interfaces import CipherBackend
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms
from .utils import _load_all_params
from ...utils import load_nist_vectors
@pytest.mark.supported(
only_if=lambda backend: backend.cipher_supported(
algorithms.ChaCha20(b"\x00" * 32, b"0" * 16), None
),
skip_message="Does not support ChaCha20",
)
@pytest.mark.requires_backend_interface(interface=CipherBackend)
class TestChaCha20(object):
@pytest.mark.parametrize(
"vector",
_load_all_params(
os.path.join("ciphers", "ChaCha20"),
["rfc7539.txt"],
load_nist_vectors
)
)
def test_vectors(self, vector, backend):
key = binascii.unhexlify(vector["key"])
nonce = binascii.unhexlify(vector["nonce"])
ibc = struct.pack("<i", int(vector["initial_block_counter"]))
pt = binascii.unhexlify(vector["plaintext"])
encryptor = Cipher(
algorithms.ChaCha20(key, ibc + nonce), None, backend
).encryptor()
computed_ct = encryptor.update(pt) + encryptor.finalize()
assert binascii.hexlify(computed_ct) == vector["ciphertext"]
def test_buffer_protocol(self, backend):
key = bytearray(os.urandom(32))
nonce = bytearray(os.urandom(16))
cipher = Cipher(
algorithms.ChaCha20(key, nonce), None, backend
)
enc = cipher.encryptor()
ct = enc.update(bytearray(b"hello")) + enc.finalize()
dec = cipher.decryptor()
pt = dec.update(ct) + dec.finalize()
assert pt == b"hello"
def test_key_size(self):
chacha = algorithms.ChaCha20(b"0" * 32, b"0" * 16)
assert chacha.key_size == 256
def test_invalid_key_size(self):
with pytest.raises(ValueError):
algorithms.ChaCha20(b"wrongsize", b"0" * 16)
def test_invalid_nonce(self):
with pytest.raises(ValueError):
algorithms.ChaCha20(b"0" * 32, b"0")
with pytest.raises(TypeError):
algorithms.ChaCha20(b"0" * 32, object())
def test_invalid_key_type(self):
with pytest.raises(TypeError, match="key must be bytes"):
algorithms.ChaCha20(u"0" * 32, b"0" * 16)
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