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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 binascii
import os
import struct
import pytest
from cryptography.exceptions import AlreadyFinalized
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms
from ...utils import load_nist_vectors
from .utils import _load_all_params
@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",
)
class TestChaCha20:
@pytest.mark.parametrize(
"vector",
_load_all_params(
os.path.join("ciphers", "ChaCha20"),
["counter-overflow.txt", "rfc7539.txt"],
load_nist_vectors,
),
)
def test_vectors(self, vector, backend):
key = binascii.unhexlify(vector["key"])
nonce = binascii.unhexlify(vector["nonce"])
ibc = struct.pack("<Q", 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()) # type:ignore[arg-type]
def test_invalid_key_type(self):
with pytest.raises(TypeError, match="key must be bytes"):
algorithms.ChaCha20("0" * 32, b"0" * 16) # type:ignore[arg-type]
def test_partial_blocks(self, backend):
# Test that partial blocks and counter increments are handled
# correctly. Successive calls to update should return the same
# as if the entire input was passed in a single call:
# update(pt[0:n]) + update(pt[n:m]) + update(pt[m:]) == update(pt)
key = bytearray(os.urandom(32))
nonce = bytearray(os.urandom(16))
cipher = Cipher(algorithms.ChaCha20(key, nonce), None, backend)
pt = bytearray(os.urandom(96 * 3))
enc_full = cipher.encryptor()
ct_full = enc_full.update(pt)
enc_partial = cipher.encryptor()
len_partial = len(pt) // 3
ct_partial_1 = enc_partial.update(pt[:len_partial])
ct_partial_2 = enc_partial.update(pt[len_partial : len_partial * 2])
ct_partial_3 = enc_partial.update(pt[len_partial * 2 :])
assert ct_full == ct_partial_1 + ct_partial_2 + ct_partial_3
def test_reset_nonce(self, backend):
data = b"helloworld" * 10
key = b"\x00" * 32
nonce = b"\x00" * 16
nonce_alt = b"\xee" * 16
cipher = Cipher(algorithms.ChaCha20(key, nonce), None)
cipher_alt = Cipher(algorithms.ChaCha20(key, nonce_alt), None)
enc = cipher.encryptor()
ct1 = enc.update(data)
assert len(ct1) == len(data)
for _ in range(2):
enc.reset_nonce(nonce)
assert enc.update(data) == ct1
# Reset the nonce to a different value
# and check it matches with a different context
enc_alt = cipher_alt.encryptor()
ct2 = enc_alt.update(data)
enc.reset_nonce(nonce_alt)
assert enc.update(data) == ct2
enc_alt.finalize()
enc.finalize()
with pytest.raises(AlreadyFinalized):
enc.reset_nonce(nonce)
dec = cipher.decryptor()
assert dec.update(ct1) == data
for _ in range(2):
dec.reset_nonce(nonce)
assert dec.update(ct1) == data
# Reset the nonce to a different value
# and check it matches with a different context
dec_alt = cipher_alt.decryptor()
dec.reset_nonce(nonce_alt)
assert dec.update(ct2) == dec_alt.update(ct2)
dec_alt.finalize()
dec.finalize()
with pytest.raises(AlreadyFinalized):
dec.reset_nonce(nonce)
def test_nonce_reset_invalid_length(self, backend):
key = b"\x00" * 32
nonce = b"\x00" * 16
cipher = Cipher(algorithms.ChaCha20(key, nonce), None)
enc = cipher.encryptor()
with pytest.raises(ValueError):
enc.reset_nonce(nonce[:-1])
with pytest.raises(ValueError):
enc.reset_nonce(nonce + b"\x00")
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