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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 warnings
from cryptography import utils
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric.utils import Prehashed
def _evp_pkey_derive(backend, evp_pkey, peer_public_key):
ctx = backend._lib.EVP_PKEY_CTX_new(evp_pkey, backend._ffi.NULL)
backend.openssl_assert(ctx != backend._ffi.NULL)
ctx = backend._ffi.gc(ctx, backend._lib.EVP_PKEY_CTX_free)
res = backend._lib.EVP_PKEY_derive_init(ctx)
backend.openssl_assert(res == 1)
res = backend._lib.EVP_PKEY_derive_set_peer(
ctx, peer_public_key._evp_pkey
)
backend.openssl_assert(res == 1)
keylen = backend._ffi.new("size_t *")
res = backend._lib.EVP_PKEY_derive(ctx, backend._ffi.NULL, keylen)
backend.openssl_assert(res == 1)
backend.openssl_assert(keylen[0] > 0)
buf = backend._ffi.new("unsigned char[]", keylen[0])
res = backend._lib.EVP_PKEY_derive(ctx, buf, keylen)
if res != 1:
raise ValueError(
"Null shared key derived from public/private pair."
)
return backend._ffi.buffer(buf, keylen[0])[:]
def _calculate_digest_and_algorithm(backend, data, algorithm):
if not isinstance(algorithm, Prehashed):
hash_ctx = hashes.Hash(algorithm, backend)
hash_ctx.update(data)
data = hash_ctx.finalize()
else:
algorithm = algorithm._algorithm
if len(data) != algorithm.digest_size:
raise ValueError(
"The provided data must be the same length as the hash "
"algorithm's digest size."
)
return (data, algorithm)
def _check_not_prehashed(signature_algorithm):
if isinstance(signature_algorithm, Prehashed):
raise TypeError(
"Prehashed is only supported in the sign and verify methods. "
"It cannot be used with signer or verifier."
)
def _warn_sign_verify_deprecated():
warnings.warn(
"signer and verifier have been deprecated. Please use sign "
"and verify instead.",
utils.PersistentlyDeprecated2017,
stacklevel=3
)
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