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# -*- coding: utf-8 -*-
#
# Cipher/mode_ecb.py : ECB mode
#
# ===================================================================
# The contents of this file are dedicated to the public domain. To
# the extent that dedication to the public domain is not available,
# everyone is granted a worldwide, perpetual, royalty-free,
# non-exclusive license to exercise all rights associated with the
# contents of this file for any purpose whatsoever.
# No rights are reserved.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
# ===================================================================
"""
Electronic Code Book (ECB) mode.
"""
__all__ = [ 'EcbMode' ]
from Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
VoidPointer, create_string_buffer,
get_raw_buffer, SmartPointer,
c_size_t, c_uint8_ptr,
is_writeable_buffer)
raw_ecb_lib = load_pycryptodome_raw_lib("Crypto.Cipher._raw_ecb", """
int ECB_start_operation(void *cipher,
void **pResult);
int ECB_encrypt(void *ecbState,
const uint8_t *in,
uint8_t *out,
size_t data_len);
int ECB_decrypt(void *ecbState,
const uint8_t *in,
uint8_t *out,
size_t data_len);
int ECB_stop_operation(void *state);
"""
)
class EcbMode(object):
"""*Electronic Code Book (ECB)*.
This is the simplest encryption mode. Each of the plaintext blocks
is directly encrypted into a ciphertext block, independently of
any other block.
This mode is dangerous because it exposes frequency of symbols
in your plaintext. Other modes (e.g. *CBC*) should be used instead.
See `NIST SP800-38A`_ , Section 6.1.
.. _`NIST SP800-38A` : http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf
:undocumented: __init__
"""
def __init__(self, block_cipher):
"""Create a new block cipher, configured in ECB mode.
:Parameters:
block_cipher : C pointer
A smart pointer to the low-level block cipher instance.
"""
self.block_size = block_cipher.block_size
self._state = VoidPointer()
result = raw_ecb_lib.ECB_start_operation(block_cipher.get(),
self._state.address_of())
if result:
raise ValueError("Error %d while instantiating the ECB 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_ecb_lib.ECB_stop_operation)
# Memory allocated for the underlying block cipher is now owned
# by the cipher mode
block_cipher.release()
def encrypt(self, plaintext, output=None):
"""Encrypt data with the key set at initialization.
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)
This function does not add any padding to the plaintext.
:Parameters:
plaintext : bytes/bytearray/memoryview
The piece of data to encrypt.
The length must be multiple of the cipher block length.
:Keywords:
output : bytearray/memoryview
The location where the ciphertext must be written to.
If ``None``, the ciphertext is returned.
:Return:
If ``output`` is ``None``, the ciphertext is returned as ``bytes``.
Otherwise, ``None``.
"""
if output is None:
ciphertext = create_string_buffer(len(plaintext))
else:
ciphertext = output
if not is_writeable_buffer(output):
raise TypeError("output must be a bytearray or a writeable memoryview")
if len(plaintext) != len(output):
raise ValueError("output must have the same length as the input"
" (%d bytes)" % len(plaintext))
result = raw_ecb_lib.ECB_encrypt(self._state.get(),
c_uint8_ptr(plaintext),
c_uint8_ptr(ciphertext),
c_size_t(len(plaintext)))
if result:
if result == 3:
raise ValueError("Data must be aligned to block boundary in ECB mode")
raise ValueError("Error %d while encrypting in ECB mode" % result)
if output is None:
return get_raw_buffer(ciphertext)
else:
return None
def decrypt(self, ciphertext, output=None):
"""Decrypt data with the key set at initialization.
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 : bytes/bytearray/memoryview
The piece of data to decrypt.
The length must be multiple of the cipher block length.
:Keywords:
output : bytearray/memoryview
The location where the plaintext must be written to.
If ``None``, the plaintext is returned.
:Return:
If ``output`` is ``None``, the plaintext is returned as ``bytes``.
Otherwise, ``None``.
"""
if output is None:
plaintext = create_string_buffer(len(ciphertext))
else:
plaintext = output
if not is_writeable_buffer(output):
raise TypeError("output must be a bytearray or a writeable memoryview")
if len(ciphertext) != len(output):
raise ValueError("output must have the same length as the input"
" (%d bytes)" % len(plaintext))
result = raw_ecb_lib.ECB_decrypt(self._state.get(),
c_uint8_ptr(ciphertext),
c_uint8_ptr(plaintext),
c_size_t(len(ciphertext)))
if result:
if result == 3:
raise ValueError("Data must be aligned to block boundary in ECB mode")
raise ValueError("Error %d while decrypting in ECB mode" % result)
if output is None:
return get_raw_buffer(plaintext)
else:
return None
def _create_ecb_cipher(factory, **kwargs):
"""Instantiate a cipher object that performs ECB encryption/decryption.
:Parameters:
factory : module
The underlying block cipher, a module from ``Crypto.Cipher``.
All keywords are 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)
cipher_state.block_size = factory.block_size
if kwargs:
raise TypeError("Unknown parameters for ECB: %s" % str(kwargs))
return EcbMode(cipher_state)
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