Initial commit

venv/Lib/site-packages/cryptography/hazmat/primitives/kdf/concatkdf.py

@@ -0,0 +1,124 @@
+# 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 annotations
+
+import typing
+
+from cryptography import utils
+from cryptography.exceptions import AlreadyFinalized, InvalidKey
+from cryptography.hazmat.primitives import constant_time, hashes, hmac
+from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
+
+
+def _int_to_u32be(n: int) -> bytes:
+    return n.to_bytes(length=4, byteorder="big")
+
+
+def _common_args_checks(
+    algorithm: hashes.HashAlgorithm,
+    length: int,
+    otherinfo: bytes | None,
+) -> None:
+    max_length = algorithm.digest_size * (2**32 - 1)
+    if length > max_length:
+        raise ValueError(f"Cannot derive keys larger than {max_length} bits.")
+    if otherinfo is not None:
+        utils._check_bytes("otherinfo", otherinfo)
+
+
+def _concatkdf_derive(
+    key_material: bytes,
+    length: int,
+    auxfn: typing.Callable[[], hashes.HashContext],
+    otherinfo: bytes,
+) -> bytes:
+    utils._check_byteslike("key_material", key_material)
+    output = [b""]
+    outlen = 0
+    counter = 1
+
+    while length > outlen:
+        h = auxfn()
+        h.update(_int_to_u32be(counter))
+        h.update(key_material)
+        h.update(otherinfo)
+        output.append(h.finalize())
+        outlen += len(output[-1])
+        counter += 1
+
+    return b"".join(output)[:length]
+
+
+class ConcatKDFHash(KeyDerivationFunction):
+    def __init__(
+        self,
+        algorithm: hashes.HashAlgorithm,
+        length: int,
+        otherinfo: bytes | None,
+        backend: typing.Any = None,
+    ):
+        _common_args_checks(algorithm, length, otherinfo)
+        self._algorithm = algorithm
+        self._length = length
+        self._otherinfo: bytes = otherinfo if otherinfo is not None else b""
+
+        self._used = False
+
+    def _hash(self) -> hashes.Hash:
+        return hashes.Hash(self._algorithm)
+
+    def derive(self, key_material: bytes) -> bytes:
+        if self._used:
+            raise AlreadyFinalized
+        self._used = True
+        return _concatkdf_derive(
+            key_material, self._length, self._hash, self._otherinfo
+        )
+
+    def verify(self, key_material: bytes, expected_key: bytes) -> None:
+        if not constant_time.bytes_eq(self.derive(key_material), expected_key):
+            raise InvalidKey
+
+
+class ConcatKDFHMAC(KeyDerivationFunction):
+    def __init__(
+        self,
+        algorithm: hashes.HashAlgorithm,
+        length: int,
+        salt: bytes | None,
+        otherinfo: bytes | None,
+        backend: typing.Any = None,
+    ):
+        _common_args_checks(algorithm, length, otherinfo)
+        self._algorithm = algorithm
+        self._length = length
+        self._otherinfo: bytes = otherinfo if otherinfo is not None else b""
+
+        if algorithm.block_size is None:
+            raise TypeError(f"{algorithm.name} is unsupported for ConcatKDF")
+
+        if salt is None:
+            salt = b"\x00" * algorithm.block_size
+        else:
+            utils._check_bytes("salt", salt)
+
+        self._salt = salt
+
+        self._used = False
+
+    def _hmac(self) -> hmac.HMAC:
+        return hmac.HMAC(self._salt, self._algorithm)
+
+    def derive(self, key_material: bytes) -> bytes:
+        if self._used:
+            raise AlreadyFinalized
+        self._used = True
+        return _concatkdf_derive(
+            key_material, self._length, self._hmac, self._otherinfo
+        )
+
+    def verify(self, key_material: bytes, expected_key: bytes) -> None:
+        if not constant_time.bytes_eq(self.derive(key_material), expected_key):
+            raise InvalidKey