added v3

venv/lib/python3.11/site-packages/cryptography/hazmat/primitives/keywrap.py

@@ -0,0 +1,177 @@
+# 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.hazmat.primitives.ciphers import Cipher
+from cryptography.hazmat.primitives.ciphers.algorithms import AES
+from cryptography.hazmat.primitives.ciphers.modes import ECB
+from cryptography.hazmat.primitives.constant_time import bytes_eq
+
+
+def _wrap_core(
+    wrapping_key: bytes,
+    a: bytes,
+    r: list[bytes],
+) -> bytes:
+    # RFC 3394 Key Wrap - 2.2.1 (index method)
+    encryptor = Cipher(AES(wrapping_key), ECB()).encryptor()
+    n = len(r)
+    for j in range(6):
+        for i in range(n):
+            # every encryption operation is a discrete 16 byte chunk (because
+            # AES has a 128-bit block size) and since we're using ECB it is
+            # safe to reuse the encryptor for the entire operation
+            b = encryptor.update(a + r[i])
+            a = (
+                int.from_bytes(b[:8], byteorder="big") ^ ((n * j) + i + 1)
+            ).to_bytes(length=8, byteorder="big")
+            r[i] = b[-8:]
+
+    assert encryptor.finalize() == b""
+
+    return a + b"".join(r)
+
+
+def aes_key_wrap(
+    wrapping_key: bytes,
+    key_to_wrap: bytes,
+    backend: typing.Any = None,
+) -> bytes:
+    if len(wrapping_key) not in [16, 24, 32]:
+        raise ValueError("The wrapping key must be a valid AES key length")
+
+    if len(key_to_wrap) < 16:
+        raise ValueError("The key to wrap must be at least 16 bytes")
+
+    if len(key_to_wrap) % 8 != 0:
+        raise ValueError("The key to wrap must be a multiple of 8 bytes")
+
+    a = b"\xa6\xa6\xa6\xa6\xa6\xa6\xa6\xa6"
+    r = [key_to_wrap[i : i + 8] for i in range(0, len(key_to_wrap), 8)]
+    return _wrap_core(wrapping_key, a, r)
+
+
+def _unwrap_core(
+    wrapping_key: bytes,
+    a: bytes,
+    r: list[bytes],
+) -> tuple[bytes, list[bytes]]:
+    # Implement RFC 3394 Key Unwrap - 2.2.2 (index method)
+    decryptor = Cipher(AES(wrapping_key), ECB()).decryptor()
+    n = len(r)
+    for j in reversed(range(6)):
+        for i in reversed(range(n)):
+            atr = (
+                int.from_bytes(a, byteorder="big") ^ ((n * j) + i + 1)
+            ).to_bytes(length=8, byteorder="big") + r[i]
+            # every decryption operation is a discrete 16 byte chunk so
+            # it is safe to reuse the decryptor for the entire operation
+            b = decryptor.update(atr)
+            a = b[:8]
+            r[i] = b[-8:]
+
+    assert decryptor.finalize() == b""
+    return a, r
+
+
+def aes_key_wrap_with_padding(
+    wrapping_key: bytes,
+    key_to_wrap: bytes,
+    backend: typing.Any = None,
+) -> bytes:
+    if len(wrapping_key) not in [16, 24, 32]:
+        raise ValueError("The wrapping key must be a valid AES key length")
+
+    aiv = b"\xa6\x59\x59\xa6" + len(key_to_wrap).to_bytes(
+        length=4, byteorder="big"
+    )
+    # pad the key to wrap if necessary
+    pad = (8 - (len(key_to_wrap) % 8)) % 8
+    key_to_wrap = key_to_wrap + b"\x00" * pad
+    if len(key_to_wrap) == 8:
+        # RFC 5649 - 4.1 - exactly 8 octets after padding
+        encryptor = Cipher(AES(wrapping_key), ECB()).encryptor()
+        b = encryptor.update(aiv + key_to_wrap)
+        assert encryptor.finalize() == b""
+        return b
+    else:
+        r = [key_to_wrap[i : i + 8] for i in range(0, len(key_to_wrap), 8)]
+        return _wrap_core(wrapping_key, aiv, r)
+
+
+def aes_key_unwrap_with_padding(
+    wrapping_key: bytes,
+    wrapped_key: bytes,
+    backend: typing.Any = None,
+) -> bytes:
+    if len(wrapped_key) < 16:
+        raise InvalidUnwrap("Must be at least 16 bytes")
+
+    if len(wrapping_key) not in [16, 24, 32]:
+        raise ValueError("The wrapping key must be a valid AES key length")
+
+    if len(wrapped_key) == 16:
+        # RFC 5649 - 4.2 - exactly two 64-bit blocks
+        decryptor = Cipher(AES(wrapping_key), ECB()).decryptor()
+        out = decryptor.update(wrapped_key)
+        assert decryptor.finalize() == b""
+        a = out[:8]
+        data = out[8:]
+        n = 1
+    else:
+        r = [wrapped_key[i : i + 8] for i in range(0, len(wrapped_key), 8)]
+        encrypted_aiv = r.pop(0)
+        n = len(r)
+        a, r = _unwrap_core(wrapping_key, encrypted_aiv, r)
+        data = b"".join(r)
+
+    # 1) Check that MSB(32,A) = A65959A6.
+    # 2) Check that 8*(n-1) < LSB(32,A) <= 8*n.  If so, let
+    #    MLI = LSB(32,A).
+    # 3) Let b = (8*n)-MLI, and then check that the rightmost b octets of
+    #    the output data are zero.
+    mli = int.from_bytes(a[4:], byteorder="big")
+    b = (8 * n) - mli
+    if (
+        not bytes_eq(a[:4], b"\xa6\x59\x59\xa6")
+        or not 8 * (n - 1) < mli <= 8 * n
+        or (b != 0 and not bytes_eq(data[-b:], b"\x00" * b))
+    ):
+        raise InvalidUnwrap()
+
+    if b == 0:
+        return data
+    else:
+        return data[:-b]
+
+
+def aes_key_unwrap(
+    wrapping_key: bytes,
+    wrapped_key: bytes,
+    backend: typing.Any = None,
+) -> bytes:
+    if len(wrapped_key) < 24:
+        raise InvalidUnwrap("Must be at least 24 bytes")
+
+    if len(wrapped_key) % 8 != 0:
+        raise InvalidUnwrap("The wrapped key must be a multiple of 8 bytes")
+
+    if len(wrapping_key) not in [16, 24, 32]:
+        raise ValueError("The wrapping key must be a valid AES key length")
+
+    aiv = b"\xa6\xa6\xa6\xa6\xa6\xa6\xa6\xa6"
+    r = [wrapped_key[i : i + 8] for i in range(0, len(wrapped_key), 8)]
+    a = r.pop(0)
+    a, r = _unwrap_core(wrapping_key, a, r)
+    if not bytes_eq(a, aiv):
+        raise InvalidUnwrap()
+
+    return b"".join(r)
+
+
+class InvalidUnwrap(Exception):
+    pass