288 lines
10 KiB
Python
288 lines
10 KiB
Python
|
# ===================================================================
|
||
|
|
#
|
||
|
|
# Copyright (c) 2014, Legrandin <helderijs@gmail.com>
|
||
|
|
# All rights reserved.
|
||
|
|
#
|
||
|
|
# Redistribution and use in source and binary forms, with or without
|
||
|
|
# modification, are permitted provided that the following conditions
|
||
|
|
# are met:
|
||
|
|
#
|
||
|
|
# 1. Redistributions of source code must retain the above copyright
|
||
|
|
# notice, this list of conditions and the following disclaimer.
|
||
|
|
# 2. Redistributions in binary form must reproduce the above copyright
|
||
|
|
# notice, this list of conditions and the following disclaimer in
|
||
|
|
# the documentation and/or other materials provided with the
|
||
|
|
# distribution.
|
||
|
|
#
|
||
|
|
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
||
|
|
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
||
|
|
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
|
||
|
|
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
|
||
|
|
# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
||
|
|
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
|
||
|
|
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
|
||
|
|
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
|
||
|
|
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
||
|
|
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
|
||
|
|
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
||
|
|
# POSSIBILITY OF SUCH DAMAGE.
|
||
|
|
# ===================================================================
|
||
|
|
|
||
|
|
from Cryptodome.Random import get_random_bytes
|
||
|
|
|
||
|
|
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, c_ulong,
|
||
|
|
is_writeable_buffer)
|
||
|
|
|
||
|
|
_raw_chacha20_lib = load_pycryptodome_raw_lib("Cryptodome.Cipher._chacha20",
|
||
|
|
"""
|
||
|
|
int chacha20_init(void **pState,
|
||
|
|
const uint8_t *key,
|
||
|
|
size_t keySize,
|
||
|
|
const uint8_t *nonce,
|
||
|
|
size_t nonceSize);
|
||
|
|
|
||
|
|
int chacha20_destroy(void *state);
|
||
|
|
|
||
|
|
int chacha20_encrypt(void *state,
|
||
|
|
const uint8_t in[],
|
||
|
|
uint8_t out[],
|
||
|
|
size_t len);
|
||
|
|
|
||
|
|
int chacha20_seek(void *state,
|
||
|
|
unsigned long block_high,
|
||
|
|
unsigned long block_low,
|
||
|
|
unsigned offset);
|
||
|
|
int hchacha20( const uint8_t key[32],
|
||
|
|
const uint8_t nonce16[16],
|
||
|
|
uint8_t subkey[32]);
|
||
|
|
""")
|
||
|
|
|
||
|
|
|
||
|
|
def _HChaCha20(key, nonce):
|
||
|
|
|
||
|
|
assert(len(key) == 32)
|
||
|
|
assert(len(nonce) == 16)
|
||
|
|
|
||
|
|
subkey = bytearray(32)
|
||
|
|
result = _raw_chacha20_lib.hchacha20(
|
||
|
|
c_uint8_ptr(key),
|
||
|
|
c_uint8_ptr(nonce),
|
||
|
|
c_uint8_ptr(subkey))
|
||
|
|
if result:
|
||
|
|
raise ValueError("Error %d when deriving subkey with HChaCha20" % result)
|
||
|
|
|
||
|
|
return subkey
|
||
|
|
|
||
|
|
|
||
|
|
class ChaCha20Cipher(object):
|
||
|
|
"""ChaCha20 (or XChaCha20) cipher object.
|
||
|
|
Do not create it directly. Use :py:func:`new` instead.
|
||
|
|
|
||
|
|
:var nonce: The nonce with length 8, 12 or 24 bytes
|
||
|
|
:vartype nonce: bytes
|
||
|
|
"""
|
||
|
|
|
||
|
|
block_size = 1
|
||
|
|
|
||
|
|
def __init__(self, key, nonce):
|
||
|
|
"""Initialize a ChaCha20/XChaCha20 cipher object
|
||
|
|
|
||
|
|
See also `new()` at the module level."""
|
||
|
|
|
||
|
|
self.nonce = _copy_bytes(None, None, nonce)
|
||
|
|
|
||
|
|
# XChaCha20 requires a key derivation with HChaCha20
|
||
|
|
# See 2.3 in https://tools.ietf.org/html/draft-arciszewski-xchacha-03
|
||
|
|
if len(nonce) == 24:
|
||
|
|
key = _HChaCha20(key, nonce[:16])
|
||
|
|
nonce = b'\x00' * 4 + nonce[16:]
|
||
|
|
self._name = "XChaCha20"
|
||
|
|
else:
|
||
|
|
self._name = "ChaCha20"
|
||
|
|
nonce = self.nonce
|
||
|
|
|
||
|
|
self._next = ("encrypt", "decrypt")
|
||
|
|
|
||
|
|
self._state = VoidPointer()
|
||
|
|
result = _raw_chacha20_lib.chacha20_init(
|
||
|
|
self._state.address_of(),
|
||
|
|
c_uint8_ptr(key),
|
||
|
|
c_size_t(len(key)),
|
||
|
|
nonce,
|
||
|
|
c_size_t(len(nonce)))
|
||
|
|
if result:
|
||
|
|
raise ValueError("Error %d instantiating a %s cipher" % (result,
|
||
|
|
self._name))
|
||
|
|
self._state = SmartPointer(self._state.get(),
|
||
|
|
_raw_chacha20_lib.chacha20_destroy)
|
||
|
|
|
||
|
|
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 "encrypt" not in self._next:
|
||
|
|
raise TypeError("Cipher object can only be used for decryption")
|
||
|
|
self._next = ("encrypt",)
|
||
|
|
return self._encrypt(plaintext, output)
|
||
|
|
|
||
|
|
def _encrypt(self, plaintext, output):
|
||
|
|
"""Encrypt without FSM checks"""
|
||
|
|
|
||
|
|
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_chacha20_lib.chacha20_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 %s" % (result, self._name))
|
||
|
|
|
||
|
|
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``.
|
||
|
|
"""
|
||
|
|
|
||
|
|
if "decrypt" not in self._next:
|
||
|
|
raise TypeError("Cipher object can only be used for encryption")
|
||
|
|
self._next = ("decrypt",)
|
||
|
|
|
||
|
|
try:
|
||
|
|
return self._encrypt(ciphertext, output)
|
||
|
|
except ValueError as e:
|
||
|
|
raise ValueError(str(e).replace("enc", "dec"))
|
||
|
|
|
||
|
|
def seek(self, position):
|
||
|
|
"""Seek to a certain position in the key stream.
|
||
|
|
|
||
|
|
Args:
|
||
|
|
position (integer):
|
||
|
|
The absolute position within the key stream, in bytes.
|
||
|
|
"""
|
||
|
|
|
||
|
|
position, offset = divmod(position, 64)
|
||
|
|
block_low = position & 0xFFFFFFFF
|
||
|
|
block_high = position >> 32
|
||
|
|
|
||
|
|
result = _raw_chacha20_lib.chacha20_seek(
|
||
|
|
self._state.get(),
|
||
|
|
c_ulong(block_high),
|
||
|
|
c_ulong(block_low),
|
||
|
|
offset
|
||
|
|
)
|
||
|
|
if result:
|
||
|
|
raise ValueError("Error %d while seeking with %s" % (result, self._name))
|
||
|
|
|
||
|
|
|
||
|
|
def _derive_Poly1305_key_pair(key, nonce):
|
||
|
|
"""Derive a tuple (r, s, nonce) for a Poly1305 MAC.
|
||
|
|
|
||
|
|
If nonce is ``None``, a new 12-byte nonce is generated.
|
||
|
|
"""
|
||
|
|
|
||
|
|
if len(key) != 32:
|
||
|
|
raise ValueError("Poly1305 with ChaCha20 requires a 32-byte key")
|
||
|
|
|
||
|
|
if nonce is None:
|
||
|
|
padded_nonce = nonce = get_random_bytes(12)
|
||
|
|
elif len(nonce) == 8:
|
||
|
|
# See RFC7538, 2.6: [...] ChaCha20 as specified here requires a 96-bit
|
||
|
|
# nonce. So if the provided nonce is only 64-bit, then the first 32
|
||
|
|
# bits of the nonce will be set to a constant number.
|
||
|
|
# This will usually be zero, but for protocols with multiple senders it may be
|
||
|
|
# different for each sender, but should be the same for all
|
||
|
|
# invocations of the function with the same key by a particular
|
||
|
|
# sender.
|
||
|
|
padded_nonce = b'\x00\x00\x00\x00' + nonce
|
||
|
|
elif len(nonce) == 12:
|
||
|
|
padded_nonce = nonce
|
||
|
|
else:
|
||
|
|
raise ValueError("Poly1305 with ChaCha20 requires an 8- or 12-byte nonce")
|
||
|
|
|
||
|
|
rs = new(key=key, nonce=padded_nonce).encrypt(b'\x00' * 32)
|
||
|
|
return rs[:16], rs[16:], nonce
|
||
|
|
|
||
|
|
|
||
|
|
def new(**kwargs):
|
||
|
|
"""Create a new ChaCha20 or XChaCha20 cipher
|
||
|
|
|
||
|
|
Keyword Args:
|
||
|
|
key (bytes/bytearray/memoryview): The secret key to use.
|
||
|
|
It must be 32 bytes long.
|
||
|
|
nonce (bytes/bytearray/memoryview): A mandatory value that
|
||
|
|
must never be reused for any other encryption
|
||
|
|
done with this key.
|
||
|
|
|
||
|
|
For ChaCha20, it must be 8 or 12 bytes long.
|
||
|
|
|
||
|
|
For XChaCha20, it must be 24 bytes long.
|
||
|
|
|
||
|
|
If not provided, 8 bytes will be randomly generated
|
||
|
|
(you can find them back in the ``nonce`` attribute).
|
||
|
|
|
||
|
|
:Return: a :class:`Cryptodome.Cipher.ChaCha20.ChaCha20Cipher` object
|
||
|
|
"""
|
||
|
|
|
||
|
|
try:
|
||
|
|
key = kwargs.pop("key")
|
||
|
|
except KeyError as e:
|
||
|
|
raise TypeError("Missing parameter %s" % e)
|
||
|
|
|
||
|
|
nonce = kwargs.pop("nonce", None)
|
||
|
|
if nonce is None:
|
||
|
|
nonce = get_random_bytes(8)
|
||
|
|
|
||
|
|
if len(key) != 32:
|
||
|
|
raise ValueError("ChaCha20/XChaCha20 key must be 32 bytes long")
|
||
|
|
|
||
|
|
if len(nonce) not in (8, 12, 24):
|
||
|
|
raise ValueError("Nonce must be 8/12 bytes(ChaCha20) or 24 bytes (XChaCha20)")
|
||
|
|
|
||
|
|
if kwargs:
|
||
|
|
raise TypeError("Unknown parameters: " + str(kwargs))
|
||
|
|
|
||
|
|
return ChaCha20Cipher(key, nonce)
|
||
|
|
|
||
|
|
# Size of a data block (in bytes)
|
||
|
|
block_size = 1
|
||
|
|
|
||
|
|
# Size of a key (in bytes)
|
||
|
|
key_size = 32
|