second commit

venv/Lib/site-packages/cryptography/hazmat/backends/openssl/utils.py

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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 typing
+
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.asymmetric.utils import Prehashed
+
+if typing.TYPE_CHECKING:
+    from cryptography.hazmat.backends.openssl.backend import Backend
+
+
+def _evp_pkey_derive(backend: "Backend", evp_pkey, peer_public_key) -> bytes:
+    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:
+        errors_with_text = backend._consume_errors_with_text()
+        raise ValueError("Error computing shared key.", errors_with_text)
+
+    return backend._ffi.buffer(buf, keylen[0])[:]
+
+
+def _calculate_digest_and_algorithm(
+    data: bytes,
+    algorithm: typing.Union[Prehashed, hashes.HashAlgorithm],
+) -> typing.Tuple[bytes, hashes.HashAlgorithm]:
+    if not isinstance(algorithm, Prehashed):
+        hash_ctx = hashes.Hash(algorithm)
+        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)