248 lines
8.7 KiB
Python
248 lines
8.7 KiB
Python
|
# ===================================================================
|
||
|
|
#
|
||
|
|
# Copyright (c) 2014, Legrandin <helderijs@gmail.com>
|
||
|
|
# All rights reserved.
|
||
|
|
#
|
||
|
|
# Redistribution and use in source and binary forms, with or without
|
||
|
|
# modification, are permitted provided that the following conditions
|
||
|
|
# are met:
|
||
|
|
#
|
||
|
|
# 1. Redistributions of source code must retain the above copyright
|
||
|
|
# notice, this list of conditions and the following disclaimer.
|
||
|
|
# 2. Redistributions in binary form must reproduce the above copyright
|
||
|
|
# notice, this list of conditions and the following disclaimer in
|
||
|
|
# the documentation and/or other materials provided with the
|
||
|
|
# distribution.
|
||
|
|
#
|
||
|
|
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
||
|
|
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
||
|
|
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
|
||
|
|
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
|
||
|
|
# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
||
|
|
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
|
||
|
|
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
|
||
|
|
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
|
||
|
|
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
||
|
|
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
|
||
|
|
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
||
|
|
# POSSIBILITY OF SUCH DAMAGE.
|
||
|
|
# ===================================================================
|
||
|
|
|
||
|
|
"""
|
||
|
|
Ciphertext Block Chaining (CBC) mode.
|
||
|
|
"""
|
||
|
|
|
||
|
|
__all__ = ['CbcMode']
|
||
|
|
|
||
|
|
from Crypto.Util._raw_api import (load_pycryptodome_raw_lib, VoidPointer,
|
||
|
|
create_string_buffer, get_raw_buffer,
|
||
|
|
SmartPointer, c_size_t, expect_byte_string)
|
||
|
|
|
||
|
|
from Crypto.Random import get_random_bytes
|
||
|
|
|
||
|
|
raw_cbc_lib = load_pycryptodome_raw_lib("Crypto.Cipher._raw_cbc", """
|
||
|
|
int CBC_start_operation(void *cipher,
|
||
|
|
const uint8_t iv[],
|
||
|
|
size_t iv_len,
|
||
|
|
void **pResult);
|
||
|
|
int CBC_encrypt(void *cbcState,
|
||
|
|
const uint8_t *in,
|
||
|
|
uint8_t *out,
|
||
|
|
size_t data_len);
|
||
|
|
int CBC_decrypt(void *cbcState,
|
||
|
|
const uint8_t *in,
|
||
|
|
uint8_t *out,
|
||
|
|
size_t data_len);
|
||
|
|
int CBC_stop_operation(void *state);
|
||
|
|
"""
|
||
|
|
)
|
||
|
|
|
||
|
|
|
||
|
|
class CbcMode(object):
|
||
|
|
"""*Cipher-Block Chaining (CBC)*.
|
||
|
|
|
||
|
|
Each of the ciphertext blocks depends on the current
|
||
|
|
and all previous plaintext blocks.
|
||
|
|
|
||
|
|
An Initialization Vector (*IV*) is required.
|
||
|
|
|
||
|
|
See `NIST SP800-38A`_ , Section 6.2 .
|
||
|
|
|
||
|
|
.. _`NIST SP800-38A` : http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf
|
||
|
|
|
||
|
|
:undocumented: __init__
|
||
|
|
"""
|
||
|
|
|
||
|
|
def __init__(self, block_cipher, iv):
|
||
|
|
"""Create a new block cipher, configured in CBC mode.
|
||
|
|
|
||
|
|
:Parameters:
|
||
|
|
block_cipher : C pointer
|
||
|
|
A smart pointer to the low-level block cipher instance.
|
||
|
|
|
||
|
|
iv : byte string
|
||
|
|
The initialization vector to use for encryption or decryption.
|
||
|
|
It is as long as the cipher block.
|
||
|
|
|
||
|
|
**The IV must be unpredictable**. Ideally it is picked randomly.
|
||
|
|
|
||
|
|
Reusing the *IV* for encryptions performed with the same key
|
||
|
|
compromises confidentiality.
|
||
|
|
"""
|
||
|
|
|
||
|
|
expect_byte_string(iv)
|
||
|
|
self._state = VoidPointer()
|
||
|
|
result = raw_cbc_lib.CBC_start_operation(block_cipher.get(),
|
||
|
|
iv,
|
||
|
|
c_size_t(len(iv)),
|
||
|
|
self._state.address_of())
|
||
|
|
if result:
|
||
|
|
raise ValueError("Error %d while instatiating the CBC mode"
|
||
|
|
% result)
|
||
|
|
|
||
|
|
# Ensure that object disposal of this Python object will (eventually)
|
||
|
|
# free the memory allocated by the raw library for the cipher mode
|
||
|
|
self._state = SmartPointer(self._state.get(),
|
||
|
|
raw_cbc_lib.CBC_stop_operation)
|
||
|
|
|
||
|
|
# Memory allocated for the underlying block cipher is now owed
|
||
|
|
# by the cipher mode
|
||
|
|
block_cipher.release()
|
||
|
|
|
||
|
|
self.block_size = len(iv)
|
||
|
|
"""The block size of the underlying cipher, in bytes."""
|
||
|
|
|
||
|
|
self.iv = iv
|
||
|
|
"""The Initialization Vector originally used to create the object.
|
||
|
|
The value does not change."""
|
||
|
|
|
||
|
|
self.IV = iv
|
||
|
|
"""Alias for `iv`"""
|
||
|
|
|
||
|
|
self._next = [ self.encrypt, self.decrypt ]
|
||
|
|
|
||
|
|
def encrypt(self, plaintext):
|
||
|
|
"""Encrypt data with the key and the parameters set at initialization.
|
||
|
|
|
||
|
|
A cipher object is stateful: once you have encrypted a message
|
||
|
|
you cannot encrypt (or decrypt) another message using the same
|
||
|
|
object.
|
||
|
|
|
||
|
|
The data to encrypt can be broken up in two or
|
||
|
|
more pieces and `encrypt` can be called multiple times.
|
||
|
|
|
||
|
|
That is, the statement:
|
||
|
|
|
||
|
|
>>> c.encrypt(a) + c.encrypt(b)
|
||
|
|
|
||
|
|
is equivalent to:
|
||
|
|
|
||
|
|
>>> c.encrypt(a+b)
|
||
|
|
|
||
|
|
That also means that you cannot reuse an object for encrypting
|
||
|
|
or decrypting other data with the same key.
|
||
|
|
|
||
|
|
This function does not add any padding to the plaintext.
|
||
|
|
|
||
|
|
:Parameters:
|
||
|
|
plaintext : byte string
|
||
|
|
The piece of data to encrypt.
|
||
|
|
Its lenght must be multiple of the cipher block size.
|
||
|
|
:Return:
|
||
|
|
the encrypted data, as a byte string.
|
||
|
|
It is as long as *plaintext*.
|
||
|
|
"""
|
||
|
|
|
||
|
|
if self.encrypt not in self._next:
|
||
|
|
raise TypeError("encrypt() cannot be called after decrypt()")
|
||
|
|
self._next = [ self.encrypt ]
|
||
|
|
|
||
|
|
expect_byte_string(plaintext)
|
||
|
|
ciphertext = create_string_buffer(len(plaintext))
|
||
|
|
result = raw_cbc_lib.CBC_encrypt(self._state.get(),
|
||
|
|
plaintext,
|
||
|
|
ciphertext,
|
||
|
|
c_size_t(len(plaintext)))
|
||
|
|
if result:
|
||
|
|
raise ValueError("Error %d while encrypting in CBC mode" % result)
|
||
|
|
return get_raw_buffer(ciphertext)
|
||
|
|
|
||
|
|
def decrypt(self, ciphertext):
|
||
|
|
"""Decrypt data with the key and the parameters set at initialization.
|
||
|
|
|
||
|
|
A cipher object is stateful: once you have decrypted a message
|
||
|
|
you cannot decrypt (or encrypt) another message with the same
|
||
|
|
object.
|
||
|
|
|
||
|
|
The data to decrypt can be broken up in two or
|
||
|
|
more pieces and `decrypt` can be called multiple times.
|
||
|
|
|
||
|
|
That is, the statement:
|
||
|
|
|
||
|
|
>>> c.decrypt(a) + c.decrypt(b)
|
||
|
|
|
||
|
|
is equivalent to:
|
||
|
|
|
||
|
|
>>> c.decrypt(a+b)
|
||
|
|
|
||
|
|
This function does not remove any padding from the plaintext.
|
||
|
|
|
||
|
|
:Parameters:
|
||
|
|
ciphertext : byte string
|
||
|
|
The piece of data to decrypt.
|
||
|
|
Its length must be multiple of the cipher block size.
|
||
|
|
|
||
|
|
:Return: the decrypted data (byte string).
|
||
|
|
"""
|
||
|
|
|
||
|
|
if self.decrypt not in self._next:
|
||
|
|
raise TypeError("decrypt() cannot be called after encrypt()")
|
||
|
|
self._next = [ self.decrypt ]
|
||
|
|
|
||
|
|
expect_byte_string(ciphertext)
|
||
|
|
plaintext = create_string_buffer(len(ciphertext))
|
||
|
|
result = raw_cbc_lib.CBC_decrypt(self._state.get(),
|
||
|
|
ciphertext,
|
||
|
|
plaintext,
|
||
|
|
c_size_t(len(ciphertext)))
|
||
|
|
if result:
|
||
|
|
raise ValueError("Error %d while decrypting in CBC mode" % result)
|
||
|
|
return get_raw_buffer(plaintext)
|
||
|
|
|
||
|
|
|
||
|
|
def _create_cbc_cipher(factory, **kwargs):
|
||
|
|
"""Instantiate a cipher object that performs CBC encryption/decryption.
|
||
|
|
|
||
|
|
:Parameters:
|
||
|
|
factory : module
|
||
|
|
The underlying block cipher, a module from ``Crypto.Cipher``.
|
||
|
|
|
||
|
|
:Keywords:
|
||
|
|
iv : byte string
|
||
|
|
The IV to use for CBC.
|
||
|
|
|
||
|
|
IV : byte string
|
||
|
|
Alias for ``iv``.
|
||
|
|
|
||
|
|
Any other keyword will be passed to the underlying block cipher.
|
||
|
|
See the relevant documentation for details (at least ``key`` will need
|
||
|
|
to be present).
|
||
|
|
"""
|
||
|
|
|
||
|
|
cipher_state = factory._create_base_cipher(kwargs)
|
||
|
|
iv = kwargs.pop("IV", None)
|
||
|
|
IV = kwargs.pop("iv", None)
|
||
|
|
|
||
|
|
if (None, None) == (iv, IV):
|
||
|
|
iv = get_random_bytes(factory.block_size)
|
||
|
|
if iv is not None:
|
||
|
|
if IV is not None:
|
||
|
|
raise TypeError("You must either use 'iv' or 'IV', not both")
|
||
|
|
else:
|
||
|
|
iv = IV
|
||
|
|
|
||
|
|
if kwargs:
|
||
|
|
raise TypeError("Unknown parameters for CBC: %s" % str(kwargs))
|
||
|
|
|
||
|
|
return CbcMode(cipher_state, iv)
|