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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 Cryptodome.Util.py3compat import _copy_bytes
from Cryptodome.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 Cryptodome.Random import get_random_bytes
_raw_salsa20_lib = load_pycryptodome_raw_lib("Cryptodome.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:`Cryptodome.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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