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| # -*- 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 Crypto.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("Crypto.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:`Crypto.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) | |