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