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- # -*- coding: utf-8 -*-
- #
- # Cipher/Salsa20.py : Salsa20 stream cipher (http://cr.yp.to/snuffle.html)
- #
- # Contributed by Fabrizio Tarizzo <fabrizio@fabriziotarizzo.org>.
- #
- # ===================================================================
- # 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 tls.Crypto.Util.py3compat import _copy_bytes
- from tls.Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
- create_string_buffer,
- get_raw_buffer, VoidPointer,
- SmartPointer, c_size_t,
- c_uint8_ptr, is_writeable_buffer)
- from tls.Crypto.Random import get_random_bytes
- _raw_salsa20_lib = load_pycryptodome_raw_lib("Crypto.Cipher._Salsa20",
- """
- int Salsa20_stream_init(uint8_t *key, size_t keylen,
- uint8_t *nonce, size_t nonce_len,
- void **pSalsaState);
- int Salsa20_stream_destroy(void *salsaState);
- int Salsa20_stream_encrypt(void *salsaState,
- const uint8_t in[],
- uint8_t out[], size_t len);
- """)
- class Salsa20Cipher:
- """Salsa20 cipher object. Do not create it directly. Use :py:func:`new`
- instead.
- :var nonce: The nonce with length 8
- :vartype nonce: byte string
- """
- def __init__(self, key, nonce):
- """Initialize a Salsa20 cipher object
- See also `new()` at the module level."""
- if len(key) not in key_size:
- raise ValueError("Incorrect key length for Salsa20 (%d bytes)" % len(key))
- if len(nonce) != 8:
- raise ValueError("Incorrect nonce length for Salsa20 (%d bytes)" %
- len(nonce))
- self.nonce = _copy_bytes(None, None, nonce)
- self._state = VoidPointer()
- result = _raw_salsa20_lib.Salsa20_stream_init(
- c_uint8_ptr(key),
- c_size_t(len(key)),
- c_uint8_ptr(nonce),
- c_size_t(len(nonce)),
- self._state.address_of())
- if result:
- raise ValueError("Error %d instantiating a Salsa20 cipher")
- self._state = SmartPointer(self._state.get(),
- _raw_salsa20_lib.Salsa20_stream_destroy)
- self.block_size = 1
- self.key_size = len(key)
- def encrypt(self, plaintext, output=None):
- """Encrypt a piece of data.
- Args:
- plaintext(bytes/bytearray/memoryview): The data to encrypt, of any size.
- Keyword Args:
- output(bytes/bytearray/memoryview): The location where the ciphertext
- is written to. If ``None``, the ciphertext is returned.
- Returns:
- 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_salsa20_lib.Salsa20_stream_encrypt(
- self._state.get(),
- c_uint8_ptr(plaintext),
- c_uint8_ptr(ciphertext),
- c_size_t(len(plaintext)))
- if result:
- raise ValueError("Error %d while encrypting with Salsa20" % result)
- if output is None:
- return get_raw_buffer(ciphertext)
- else:
- return None
- def decrypt(self, ciphertext, output=None):
- """Decrypt a piece of data.
-
- Args:
- ciphertext(bytes/bytearray/memoryview): The data to decrypt, of any size.
- Keyword Args:
- output(bytes/bytearray/memoryview): The location where the plaintext
- is written to. If ``None``, the plaintext is returned.
- Returns:
- If ``output`` is ``None``, the plaintext is returned as ``bytes``.
- Otherwise, ``None``.
- """
- try:
- return self.encrypt(ciphertext, output=output)
- except ValueError as e:
- raise ValueError(str(e).replace("enc", "dec"))
- def new(key, nonce=None):
- """Create a new Salsa20 cipher
- :keyword key: The secret key to use. It must be 16 or 32 bytes long.
- :type key: bytes/bytearray/memoryview
- :keyword nonce:
- A value that must never be reused for any other encryption
- done with this key. It must be 8 bytes long.
- If not provided, a random byte string will be generated (you can read
- it back via the ``nonce`` attribute of the returned object).
- :type nonce: bytes/bytearray/memoryview
- :Return: a :class:`Crypto.Cipher.Salsa20.Salsa20Cipher` object
- """
- if nonce is None:
- nonce = get_random_bytes(8)
- return Salsa20Cipher(key, nonce)
- # Size of a data block (in bytes)
- block_size = 1
- # Size of a key (in bytes)
- key_size = (16, 32)
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