138 lines
5.0 KiB
Python
138 lines
5.0 KiB
Python
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# -*- coding: utf-8 -*-
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#
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# Cipher/ARC4.py : ARC4
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#
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# ===================================================================
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# The contents of this file are dedicated to the public domain. To
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# the extent that dedication to the public domain is not available,
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# everyone is granted a worldwide, perpetual, royalty-free,
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# non-exclusive license to exercise all rights associated with the
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# contents of this file for any purpose whatsoever.
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# No rights are reserved.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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# ===================================================================
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from Crypto.Util.py3compat import b
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from Crypto.Util._raw_api import (load_pycryptodome_raw_lib, VoidPointer,
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create_string_buffer, get_raw_buffer,
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SmartPointer, c_size_t, c_uint8_ptr)
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_raw_arc4_lib = load_pycryptodome_raw_lib("Crypto.Cipher._ARC4", """
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int ARC4_stream_encrypt(void *rc4State, const uint8_t in[],
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uint8_t out[], size_t len);
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int ARC4_stream_init(uint8_t *key, size_t keylen,
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void **pRc4State);
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int ARC4_stream_destroy(void *rc4State);
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""")
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class ARC4Cipher:
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"""ARC4 cipher object. Do not create it directly. Use
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:func:`Crypto.Cipher.ARC4.new` instead.
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"""
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def __init__(self, key, *args, **kwargs):
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"""Initialize an ARC4 cipher object
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See also `new()` at the module level."""
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if len(args) > 0:
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ndrop = args[0]
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args = args[1:]
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else:
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ndrop = kwargs.pop('drop', 0)
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if len(key) not in key_size:
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raise ValueError("Incorrect ARC4 key length (%d bytes)" %
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len(key))
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self._state = VoidPointer()
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result = _raw_arc4_lib.ARC4_stream_init(c_uint8_ptr(key),
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c_size_t(len(key)),
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self._state.address_of())
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if result != 0:
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raise ValueError("Error %d while creating the ARC4 cipher"
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% result)
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self._state = SmartPointer(self._state.get(),
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_raw_arc4_lib.ARC4_stream_destroy)
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if ndrop > 0:
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# This is OK even if the cipher is used for decryption,
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# since encrypt and decrypt are actually the same thing
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# with ARC4.
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self.encrypt(b'\x00' * ndrop)
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self.block_size = 1
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self.key_size = len(key)
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def encrypt(self, plaintext):
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"""Encrypt a piece of data.
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:param plaintext: The data to encrypt, of any size.
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:type plaintext: bytes, bytearray, memoryview
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:returns: the encrypted byte string, of equal length as the
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plaintext.
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"""
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ciphertext = create_string_buffer(len(plaintext))
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result = _raw_arc4_lib.ARC4_stream_encrypt(self._state.get(),
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c_uint8_ptr(plaintext),
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ciphertext,
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c_size_t(len(plaintext)))
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if result:
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raise ValueError("Error %d while encrypting with RC4" % result)
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return get_raw_buffer(ciphertext)
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def decrypt(self, ciphertext):
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"""Decrypt a piece of data.
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:param ciphertext: The data to decrypt, of any size.
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:type ciphertext: bytes, bytearray, memoryview
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:returns: the decrypted byte string, of equal length as the
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ciphertext.
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"""
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try:
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return self.encrypt(ciphertext)
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except ValueError as e:
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raise ValueError(str(e).replace("enc", "dec"))
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def new(key, *args, **kwargs):
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"""Create a new ARC4 cipher.
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:param key:
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The secret key to use in the symmetric cipher.
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Its length must be in the range ``[5..256]``.
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The recommended length is 16 bytes.
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:type key: bytes, bytearray, memoryview
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:Keyword Arguments:
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* *drop* (``integer``) --
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The amount of bytes to discard from the initial part of the keystream.
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In fact, such part has been found to be distinguishable from random
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data (while it shouldn't) and also correlated to key.
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The recommended value is 3072_ bytes. The default value is 0.
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:Return: an `ARC4Cipher` object
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.. _3072: http://eprint.iacr.org/2002/067.pdf
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"""
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return ARC4Cipher(key, *args, **kwargs)
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# Size of a data block (in bytes)
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block_size = 1
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# Size of a key (in bytes)
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key_size = range(5, 256+1)
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