added v3

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

@@ -0,0 +1,183 @@
+# 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 abc
+import typing
+
+from cryptography import utils
+from cryptography.exceptions import AlreadyFinalized
+from cryptography.hazmat.bindings._rust import (
+    PKCS7PaddingContext,
+    PKCS7UnpaddingContext,
+    check_ansix923_padding,
+)
+
+
+class PaddingContext(metaclass=abc.ABCMeta):
+    @abc.abstractmethod
+    def update(self, data: bytes) -> bytes:
+        """
+        Pads the provided bytes and returns any available data as bytes.
+        """
+
+    @abc.abstractmethod
+    def finalize(self) -> bytes:
+        """
+        Finalize the padding, returns bytes.
+        """
+
+
+def _byte_padding_check(block_size: int) -> None:
+    if not (0 <= block_size <= 2040):
+        raise ValueError("block_size must be in range(0, 2041).")
+
+    if block_size % 8 != 0:
+        raise ValueError("block_size must be a multiple of 8.")
+
+
+def _byte_padding_update(
+    buffer_: bytes | None, data: bytes, block_size: int
+) -> tuple[bytes, bytes]:
+    if buffer_ is None:
+        raise AlreadyFinalized("Context was already finalized.")
+
+    utils._check_byteslike("data", data)
+
+    buffer_ += bytes(data)
+
+    finished_blocks = len(buffer_) // (block_size // 8)
+
+    result = buffer_[: finished_blocks * (block_size // 8)]
+    buffer_ = buffer_[finished_blocks * (block_size // 8) :]
+
+    return buffer_, result
+
+
+def _byte_padding_pad(
+    buffer_: bytes | None,
+    block_size: int,
+    paddingfn: typing.Callable[[int], bytes],
+) -> bytes:
+    if buffer_ is None:
+        raise AlreadyFinalized("Context was already finalized.")
+
+    pad_size = block_size // 8 - len(buffer_)
+    return buffer_ + paddingfn(pad_size)
+
+
+def _byte_unpadding_update(
+    buffer_: bytes | None, data: bytes, block_size: int
+) -> tuple[bytes, bytes]:
+    if buffer_ is None:
+        raise AlreadyFinalized("Context was already finalized.")
+
+    utils._check_byteslike("data", data)
+
+    buffer_ += bytes(data)
+
+    finished_blocks = max(len(buffer_) // (block_size // 8) - 1, 0)
+
+    result = buffer_[: finished_blocks * (block_size // 8)]
+    buffer_ = buffer_[finished_blocks * (block_size // 8) :]
+
+    return buffer_, result
+
+
+def _byte_unpadding_check(
+    buffer_: bytes | None,
+    block_size: int,
+    checkfn: typing.Callable[[bytes], int],
+) -> bytes:
+    if buffer_ is None:
+        raise AlreadyFinalized("Context was already finalized.")
+
+    if len(buffer_) != block_size // 8:
+        raise ValueError("Invalid padding bytes.")
+
+    valid = checkfn(buffer_)
+
+    if not valid:
+        raise ValueError("Invalid padding bytes.")
+
+    pad_size = buffer_[-1]
+    return buffer_[:-pad_size]
+
+
+class PKCS7:
+    def __init__(self, block_size: int):
+        _byte_padding_check(block_size)
+        self.block_size = block_size
+
+    def padder(self) -> PaddingContext:
+        return PKCS7PaddingContext(self.block_size)
+
+    def unpadder(self) -> PaddingContext:
+        return PKCS7UnpaddingContext(self.block_size)
+
+
+PaddingContext.register(PKCS7PaddingContext)
+PaddingContext.register(PKCS7UnpaddingContext)
+
+
+class ANSIX923:
+    def __init__(self, block_size: int):
+        _byte_padding_check(block_size)
+        self.block_size = block_size
+
+    def padder(self) -> PaddingContext:
+        return _ANSIX923PaddingContext(self.block_size)
+
+    def unpadder(self) -> PaddingContext:
+        return _ANSIX923UnpaddingContext(self.block_size)
+
+
+class _ANSIX923PaddingContext(PaddingContext):
+    _buffer: bytes | None
+
+    def __init__(self, block_size: int):
+        self.block_size = block_size
+        # TODO: more copies than necessary, we should use zero-buffer (#193)
+        self._buffer = b""
+
+    def update(self, data: bytes) -> bytes:
+        self._buffer, result = _byte_padding_update(
+            self._buffer, data, self.block_size
+        )
+        return result
+
+    def _padding(self, size: int) -> bytes:
+        return bytes([0]) * (size - 1) + bytes([size])
+
+    def finalize(self) -> bytes:
+        result = _byte_padding_pad(
+            self._buffer, self.block_size, self._padding
+        )
+        self._buffer = None
+        return result
+
+
+class _ANSIX923UnpaddingContext(PaddingContext):
+    _buffer: bytes | None
+
+    def __init__(self, block_size: int):
+        self.block_size = block_size
+        # TODO: more copies than necessary, we should use zero-buffer (#193)
+        self._buffer = b""
+
+    def update(self, data: bytes) -> bytes:
+        self._buffer, result = _byte_unpadding_update(
+            self._buffer, data, self.block_size
+        )
+        return result
+
+    def finalize(self) -> bytes:
+        result = _byte_unpadding_check(
+            self._buffer,
+            self.block_size,
+            check_ansix923_padding,
+        )
+        self._buffer = None
+        return result