196 lines
6.9 KiB
Python
196 lines
6.9 KiB
Python
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# -*- coding: utf-8 -*-
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#
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# Cipher/Blowfish.py : Blowfish
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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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"""Blowfish symmetric cipher
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Blowfish_ is a symmetric block cipher designed by Bruce Schneier.
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It has a fixed data block size of 8 bytes and its keys can vary in length
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from 32 to 448 bits (4 to 56 bytes).
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Blowfish is deemed secure and it is fast. However, its keys should be chosen
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to be big enough to withstand a brute force attack (e.g. at least 16 bytes).
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**Use AES, not Blowfish. This module is provided only for legacy purposes.**
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As an example, encryption can be done as follows:
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>>> from Crypto.Cipher import Blowfish
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>>> from struct import pack
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>>>
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>>> bs = Blowfish.block_size
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>>> key = b'An arbitrarily long key'
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>>> cipher = Blowfish.new(key, Blowfish.MODE_CBC)
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>>> plaintext = b'docendo discimus '
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>>> plen = bs - len(plaintext) % bs
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>>> padding = [plen]*plen
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>>> padding = pack('b'*plen, *padding)
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>>> msg = cipher.iv + cipher.encrypt(plaintext + padding)
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.. _Blowfish: http://www.schneier.com/blowfish.html
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:undocumented: __package__
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"""
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import sys
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from Crypto.Cipher import _create_cipher
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from Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
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VoidPointer, SmartPointer, c_size_t,
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expect_byte_string)
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_raw_blowfish_lib = load_pycryptodome_raw_lib(
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"Crypto.Cipher._raw_blowfish",
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"""
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int Blowfish_start_operation(const uint8_t key[],
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size_t key_len,
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void **pResult);
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int Blowfish_encrypt(const void *state,
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const uint8_t *in,
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uint8_t *out,
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size_t data_len);
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int Blowfish_decrypt(const void *state,
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const uint8_t *in,
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uint8_t *out,
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size_t data_len);
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int Blowfish_stop_operation(void *state);
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"""
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)
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def _create_base_cipher(dict_parameters):
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"""This method instantiates and returns a smart pointer to
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a low-level base cipher. It will absorb named parameters in
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the process."""
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try:
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key = dict_parameters.pop("key")
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except KeyError:
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raise TypeError("Missing 'key' parameter")
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expect_byte_string(key)
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if len(key) not in key_size:
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raise ValueError("Incorrect Blowfish key length (%d bytes)" % len(key))
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start_operation = _raw_blowfish_lib.Blowfish_start_operation
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stop_operation = _raw_blowfish_lib.Blowfish_stop_operation
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void_p = VoidPointer()
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result = start_operation(key, c_size_t(len(key)), void_p.address_of())
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if result:
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raise ValueError("Error %X while instantiating the Blowfish cipher"
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% result)
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return SmartPointer(void_p.get(), stop_operation)
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def new(key, mode, *args, **kwargs):
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"""Create a new Blowfish cipher
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:Parameters:
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key : byte string
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The secret key to use in the symmetric cipher.
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Its length can vary from 5 to 56 bytes.
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mode : a *MODE_** constant
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The chaining mode to use for encryption or decryption.
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:Keywords:
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iv : byte string
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(*Only* `MODE_CBC`, `MODE_CFB`, `MODE_OFB`, `MODE_OPENPGP`).
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The initialization vector to use for encryption or decryption.
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For `MODE_OPENPGP`, IV must be 8 bytes long for encryption
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and 10 bytes for decryption (in the latter case, it is
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actually the *encrypted* IV which was prefixed to the ciphertext).
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For all other modes, it must be 8 bytes long.
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If not provided, a random byte string will be generated (you must
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read it back via the ``iv`` attribute).
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nonce : byte string
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(*Only* `MODE_EAX` and `MODE_CTR`).
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A value that must never be reused for any other encryption.
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For `MODE_CTR`, its length must be in the range ``[0..7]``.
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For `MODE_EAX`, there are no restrictions, but it is recommended to
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use at least 16 bytes.
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If not provided for `MODE_EAX`, a 16 byte random string will be used
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(you can read it back via the ``nonce`` attribute).
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mac_len : integer
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(*Only* `MODE_EAX`). Length of the authentication tag, in bytes.
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It must be no larger than 8 (which is the default).
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segment_size : integer
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(*Only* `MODE_CFB`).The number of bits the plaintext and ciphertext
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are segmented in. It must be a multiple of 8.
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If not specified, it will be assumed to be 8.
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initial_value : integer
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(*Only* `MODE_CTR`). The initial value for the counter within
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the counter block. By default it is 0.
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:Return: a Blowfish cipher object, of the applicable mode:
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- CBC_ mode
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- CFB_ mode
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- CTR_ mode
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- EAX_ mode
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- ECB_ mode
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- OFB_ mode
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- OpenPgp_ mode
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.. _CBC: Crypto.Cipher._mode_cbc.CbcMode-class.html
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.. _CFB: Crypto.Cipher._mode_cfb.CfbMode-class.html
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.. _CTR: Crypto.Cipher._mode_ctr.CtrMode-class.html
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.. _EAX: Crypto.Cipher._mode_eax.EaxMode-class.html
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.. _ECB: Crypto.Cipher._mode_ecb.EcbMode-class.html
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.. _OFB: Crypto.Cipher._mode_ofb.OfbMode-class.html
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.. _OpenPgp: Crypto.Cipher._mode_openpgp.OpenPgpMode-class.html
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"""
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return _create_cipher(sys.modules[__name__], key, mode, *args, **kwargs)
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#: Electronic Code Book (ECB). See `Crypto.Cipher._mode_ecb.EcbMode`.
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MODE_ECB = 1
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#: Cipher-Block Chaining (CBC). See `Crypto.Cipher._mode_cbc.CbcMode`.
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MODE_CBC = 2
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#: Cipher FeedBack (CFB). See `Crypto.Cipher._mode_cfb.CfbMode`.
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MODE_CFB = 3
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#: Output FeedBack (OFB). See `Crypto.Cipher._mode_ofb.OfbMode`.
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MODE_OFB = 5
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#: CounTer Mode (CTR). See `Crypto.Cipher._mode_ctr.CtrMode`.
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MODE_CTR = 6
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#: OpenPGP Mode. See `Crypto.Cipher._mode_openpgp.OpenPgpMode`.
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MODE_OPENPGP = 7
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#: EAX Mode. See `Crypto.Cipher._mode_eax.EaxMode`.
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MODE_EAX = 9
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#: Size of a data block (in bytes)
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block_size = 8
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#: Size of a key (in bytes)
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key_size = range(5, 56 + 1)
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