136 lines
5 KiB
Python
136 lines
5 KiB
Python
# -*- coding: utf-8 -*-
|
|
#
|
|
# Cipher/ARC4.py : ARC4
|
|
#
|
|
# ===================================================================
|
|
# 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.
|
|
# ===================================================================
|
|
|
|
from Cryptodome.Util._raw_api import (load_pycryptodome_raw_lib, VoidPointer,
|
|
create_string_buffer, get_raw_buffer,
|
|
SmartPointer, c_size_t, c_uint8_ptr)
|
|
|
|
|
|
_raw_arc4_lib = load_pycryptodome_raw_lib("Cryptodome.Cipher._ARC4", """
|
|
int ARC4_stream_encrypt(void *rc4State, const uint8_t in[],
|
|
uint8_t out[], size_t len);
|
|
int ARC4_stream_init(uint8_t *key, size_t keylen,
|
|
void **pRc4State);
|
|
int ARC4_stream_destroy(void *rc4State);
|
|
""")
|
|
|
|
|
|
class ARC4Cipher:
|
|
"""ARC4 cipher object. Do not create it directly. Use
|
|
:func:`Cryptodome.Cipher.ARC4.new` instead.
|
|
"""
|
|
|
|
def __init__(self, key, *args, **kwargs):
|
|
"""Initialize an ARC4 cipher object
|
|
|
|
See also `new()` at the module level."""
|
|
|
|
if len(args) > 0:
|
|
ndrop = args[0]
|
|
args = args[1:]
|
|
else:
|
|
ndrop = kwargs.pop('drop', 0)
|
|
|
|
if len(key) not in key_size:
|
|
raise ValueError("Incorrect ARC4 key length (%d bytes)" %
|
|
len(key))
|
|
|
|
self._state = VoidPointer()
|
|
result = _raw_arc4_lib.ARC4_stream_init(c_uint8_ptr(key),
|
|
c_size_t(len(key)),
|
|
self._state.address_of())
|
|
if result != 0:
|
|
raise ValueError("Error %d while creating the ARC4 cipher"
|
|
% result)
|
|
self._state = SmartPointer(self._state.get(),
|
|
_raw_arc4_lib.ARC4_stream_destroy)
|
|
|
|
if ndrop > 0:
|
|
# This is OK even if the cipher is used for decryption,
|
|
# since encrypt and decrypt are actually the same thing
|
|
# with ARC4.
|
|
self.encrypt(b'\x00' * ndrop)
|
|
|
|
self.block_size = 1
|
|
self.key_size = len(key)
|
|
|
|
def encrypt(self, plaintext):
|
|
"""Encrypt a piece of data.
|
|
|
|
:param plaintext: The data to encrypt, of any size.
|
|
:type plaintext: bytes, bytearray, memoryview
|
|
:returns: the encrypted byte string, of equal length as the
|
|
plaintext.
|
|
"""
|
|
|
|
ciphertext = create_string_buffer(len(plaintext))
|
|
result = _raw_arc4_lib.ARC4_stream_encrypt(self._state.get(),
|
|
c_uint8_ptr(plaintext),
|
|
ciphertext,
|
|
c_size_t(len(plaintext)))
|
|
if result:
|
|
raise ValueError("Error %d while encrypting with RC4" % result)
|
|
return get_raw_buffer(ciphertext)
|
|
|
|
def decrypt(self, ciphertext):
|
|
"""Decrypt a piece of data.
|
|
|
|
:param ciphertext: The data to decrypt, of any size.
|
|
:type ciphertext: bytes, bytearray, memoryview
|
|
:returns: the decrypted byte string, of equal length as the
|
|
ciphertext.
|
|
"""
|
|
|
|
try:
|
|
return self.encrypt(ciphertext)
|
|
except ValueError as e:
|
|
raise ValueError(str(e).replace("enc", "dec"))
|
|
|
|
|
|
def new(key, *args, **kwargs):
|
|
"""Create a new ARC4 cipher.
|
|
|
|
:param key:
|
|
The secret key to use in the symmetric cipher.
|
|
Its length must be in the range ``[1..256]``.
|
|
The recommended length is 16 bytes.
|
|
:type key: bytes, bytearray, memoryview
|
|
|
|
:Keyword Arguments:
|
|
* *drop* (``integer``) --
|
|
The amount of bytes to discard from the initial part of the keystream.
|
|
In fact, such part has been found to be distinguishable from random
|
|
data (while it shouldn't) and also correlated to key.
|
|
|
|
The recommended value is 3072_ bytes. The default value is 0.
|
|
|
|
:Return: an `ARC4Cipher` object
|
|
|
|
.. _3072: http://eprint.iacr.org/2002/067.pdf
|
|
"""
|
|
return ARC4Cipher(key, *args, **kwargs)
|
|
|
|
|
|
# Size of a data block (in bytes)
|
|
block_size = 1
|
|
# Size of a key (in bytes)
|
|
key_size = range(1, 256+1)
|