win32 platform

Lib/site-packages/cryptography/hazmat/primitives/padding.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 absolute_import, division, print_function
+
+import abc
+
+import six
+
+from cryptography import utils
+from cryptography.exceptions import AlreadyFinalized
+from cryptography.hazmat.bindings._padding import lib
+
+
+@six.add_metaclass(abc.ABCMeta)
+class PaddingContext(object):
+    @abc.abstractmethod
+    def update(self, data):
+        """
+        Pads the provided bytes and returns any available data as bytes.
+        """
+
+    @abc.abstractmethod
+    def finalize(self):
+        """
+        Finalize the padding, returns bytes.
+        """
+
+
+class PKCS7(object):
+    def __init__(self, block_size):
+        if not (0 <= block_size < 256):
+            raise ValueError("block_size must be in range(0, 256).")
+
+        if block_size % 8 != 0:
+            raise ValueError("block_size must be a multiple of 8.")
+
+        self.block_size = block_size
+
+    def padder(self):
+        return _PKCS7PaddingContext(self.block_size)
+
+    def unpadder(self):
+        return _PKCS7UnpaddingContext(self.block_size)
+
+
+@utils.register_interface(PaddingContext)
+class _PKCS7PaddingContext(object):
+    def __init__(self, block_size):
+        self.block_size = block_size
+        # TODO: more copies than necessary, we should use zero-buffer (#193)
+        self._buffer = b""
+
+    def update(self, data):
+        if self._buffer is None:
+            raise AlreadyFinalized("Context was already finalized.")
+
+        if not isinstance(data, bytes):
+            raise TypeError("data must be bytes.")
+
+        self._buffer += data
+
+        finished_blocks = len(self._buffer) // (self.block_size // 8)
+
+        result = self._buffer[:finished_blocks * (self.block_size // 8)]
+        self._buffer = self._buffer[finished_blocks * (self.block_size // 8):]
+
+        return result
+
+    def finalize(self):
+        if self._buffer is None:
+            raise AlreadyFinalized("Context was already finalized.")
+
+        pad_size = self.block_size // 8 - len(self._buffer)
+        result = self._buffer + six.int2byte(pad_size) * pad_size
+        self._buffer = None
+        return result
+
+
+@utils.register_interface(PaddingContext)
+class _PKCS7UnpaddingContext(object):
+    def __init__(self, block_size):
+        self.block_size = block_size
+        # TODO: more copies than necessary, we should use zero-buffer (#193)
+        self._buffer = b""
+
+    def update(self, data):
+        if self._buffer is None:
+            raise AlreadyFinalized("Context was already finalized.")
+
+        if not isinstance(data, bytes):
+            raise TypeError("data must be bytes.")
+
+        self._buffer += data
+
+        finished_blocks = max(
+            len(self._buffer) // (self.block_size // 8) - 1,
+            0
+        )
+
+        result = self._buffer[:finished_blocks * (self.block_size // 8)]
+        self._buffer = self._buffer[finished_blocks * (self.block_size // 8):]
+
+        return result
+
+    def finalize(self):
+        if self._buffer is None:
+            raise AlreadyFinalized("Context was already finalized.")
+
+        if len(self._buffer) != self.block_size // 8:
+            raise ValueError("Invalid padding bytes.")
+
+        valid = lib.Cryptography_check_pkcs7_padding(
+            self._buffer, self.block_size // 8
+        )
+
+        if not valid:
+            raise ValueError("Invalid padding bytes.")
+
+        pad_size = six.indexbytes(self._buffer, -1)
+        res = self._buffer[:-pad_size]
+        self._buffer = None
+        return res