64 lines
2.1 KiB
Python
64 lines
2.1 KiB
Python
# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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from __future__ import annotations
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import typing
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from cryptography.hazmat.primitives import hashes
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from cryptography.hazmat.primitives.asymmetric.utils import Prehashed
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if typing.TYPE_CHECKING:
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from cryptography.hazmat.backends.openssl.backend import Backend
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def _evp_pkey_derive(backend: Backend, evp_pkey, peer_public_key) -> bytes:
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ctx = backend._lib.EVP_PKEY_CTX_new(evp_pkey, backend._ffi.NULL)
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backend.openssl_assert(ctx != backend._ffi.NULL)
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ctx = backend._ffi.gc(ctx, backend._lib.EVP_PKEY_CTX_free)
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res = backend._lib.EVP_PKEY_derive_init(ctx)
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backend.openssl_assert(res == 1)
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if backend._lib.Cryptography_HAS_EVP_PKEY_SET_PEER_EX:
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res = backend._lib.EVP_PKEY_derive_set_peer_ex(
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ctx, peer_public_key._evp_pkey, 0
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)
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else:
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res = backend._lib.EVP_PKEY_derive_set_peer(
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ctx, peer_public_key._evp_pkey
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)
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backend.openssl_assert(res == 1)
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keylen = backend._ffi.new("size_t *")
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res = backend._lib.EVP_PKEY_derive(ctx, backend._ffi.NULL, keylen)
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backend.openssl_assert(res == 1)
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backend.openssl_assert(keylen[0] > 0)
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buf = backend._ffi.new("unsigned char[]", keylen[0])
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res = backend._lib.EVP_PKEY_derive(ctx, buf, keylen)
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if res != 1:
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errors = backend._consume_errors()
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raise ValueError("Error computing shared key.", errors)
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return backend._ffi.buffer(buf, keylen[0])[:]
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def _calculate_digest_and_algorithm(
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data: bytes,
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algorithm: typing.Union[Prehashed, hashes.HashAlgorithm],
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) -> typing.Tuple[bytes, hashes.HashAlgorithm]:
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if not isinstance(algorithm, Prehashed):
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hash_ctx = hashes.Hash(algorithm)
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hash_ctx.update(data)
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data = hash_ctx.finalize()
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else:
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algorithm = algorithm._algorithm
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if len(data) != algorithm.digest_size:
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raise ValueError(
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"The provided data must be the same length as the hash "
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"algorithm's digest size."
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)
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return (data, algorithm)
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