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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 pytest
from cryptography.exceptions import _Reasons
from cryptography.hazmat.backends.interfaces import DHBackend
from cryptography.hazmat.primitives.asymmetric.x25519 import (
X25519PrivateKey, X25519PublicKey
)
from ...utils import (
load_nist_vectors, load_vectors_from_file, raises_unsupported_algorithm
)
@pytest.mark.supported(
only_if=lambda backend: not backend.x25519_supported(),
skip_message="Requires OpenSSL without X25519 support"
)
@pytest.mark.requires_backend_interface(interface=DHBackend)
def test_x25519_unsupported(backend):
with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_EXCHANGE_ALGORITHM):
X25519PublicKey.from_public_bytes(b"0" * 32)
with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_EXCHANGE_ALGORITHM):
X25519PrivateKey.generate()
@pytest.mark.supported(
only_if=lambda backend: backend.x25519_supported(),
skip_message="Requires OpenSSL with X25519 support"
)
@pytest.mark.requires_backend_interface(interface=DHBackend)
class TestX25519Exchange(object):
@pytest.mark.parametrize(
"vector",
load_vectors_from_file(
os.path.join("asymmetric", "X25519", "rfc7748.txt"),
load_nist_vectors
)
)
def test_rfc7748(self, vector, backend):
private = binascii.unhexlify(vector["input_scalar"])
public = binascii.unhexlify(vector["input_u"])
shared_key = binascii.unhexlify(vector["output_u"])
private_key = X25519PrivateKey._from_private_bytes(private)
public_key = X25519PublicKey.from_public_bytes(public)
computed_shared_key = private_key.exchange(public_key)
assert computed_shared_key == shared_key
def test_rfc7748_1000_iteration(self, backend):
old_private = private = public = binascii.unhexlify(
b"090000000000000000000000000000000000000000000000000000000000"
b"0000"
)
shared_key = binascii.unhexlify(
b"684cf59ba83309552800ef566f2f4d3c1c3887c49360e3875f2eb94d9953"
b"2c51"
)
private_key = X25519PrivateKey._from_private_bytes(private)
public_key = X25519PublicKey.from_public_bytes(public)
for _ in range(1000):
computed_shared_key = private_key.exchange(public_key)
private_key = X25519PrivateKey._from_private_bytes(
computed_shared_key
)
public_key = X25519PublicKey.from_public_bytes(old_private)
old_private = computed_shared_key
assert computed_shared_key == shared_key
def test_null_shared_key_raises_error(self, backend):
"""
The vector used here is taken from wycheproof's x25519 test vectors
"""
public = binascii.unhexlify(
"5f9c95bca3508c24b1d0b1559c83ef5b04445cc4581c8e86d8224eddd09f1157"
)
private = binascii.unhexlify(
"78f1e8edf14481b389448dac8f59c70b038e7cf92ef2c7eff57a72466e115296"
)
private_key = X25519PrivateKey._from_private_bytes(
private
)
public_key = X25519PublicKey.from_public_bytes(public)
with pytest.raises(ValueError):
private_key.exchange(public_key)
# These vectors are also from RFC 7748
# https://tools.ietf.org/html/rfc7748#section-6.1
@pytest.mark.parametrize(
("private_bytes", "public_bytes"),
[
(
binascii.unhexlify(
b"77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba"
b"51db92c2a"
),
binascii.unhexlify(
b"8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98"
b"eaa9b4e6a"
)
),
(
binascii.unhexlify(
b"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b2"
b"7ff88e0eb"
),
binascii.unhexlify(
b"de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e1"
b"46f882b4f"
)
)
]
)
def test_public_bytes(self, private_bytes, public_bytes, backend):
private_key = X25519PrivateKey._from_private_bytes(private_bytes)
assert private_key.public_key().public_bytes() == public_bytes
public_key = X25519PublicKey.from_public_bytes(public_bytes)
assert public_key.public_bytes() == public_bytes
def test_generate(self, backend):
key = X25519PrivateKey.generate()
assert key
assert key.public_key()
def test_invalid_type_exchange(self, backend):
key = X25519PrivateKey.generate()
with pytest.raises(TypeError):
key.exchange(object())
def test_invalid_length_from_public_bytes(self, backend):
with pytest.raises(ValueError):
X25519PublicKey.from_public_bytes(b"a" * 31)
with pytest.raises(ValueError):
X25519PublicKey.from_public_bytes(b"a" * 33)
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