188 lines
6.8 KiB
Python
188 lines
6.8 KiB
Python
# -*- coding: utf-8 -*-
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#
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# Cipher/DES3.py : DES3
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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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"""
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Module's constants for the modes of operation supported with Triple DES:
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:var MODE_ECB: :ref:`Electronic Code Book (ECB) <ecb_mode>`
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:var MODE_CBC: :ref:`Cipher-Block Chaining (CBC) <cbc_mode>`
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:var MODE_CFB: :ref:`Cipher FeedBack (CFB) <cfb_mode>`
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:var MODE_OFB: :ref:`Output FeedBack (OFB) <ofb_mode>`
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:var MODE_CTR: :ref:`CounTer Mode (CTR) <ctr_mode>`
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:var MODE_OPENPGP: :ref:`OpenPGP Mode <openpgp_mode>`
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:var MODE_EAX: :ref:`EAX Mode <eax_mode>`
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"""
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import sys
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from Cryptodome.Cipher import _create_cipher
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from Cryptodome.Util.py3compat import byte_string, bchr, bord, bstr
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from Cryptodome.Util._raw_api import (load_pycryptodome_raw_lib,
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VoidPointer, SmartPointer,
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c_size_t)
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_raw_des3_lib = load_pycryptodome_raw_lib(
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"Cryptodome.Cipher._raw_des3",
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"""
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int DES3_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 DES3_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 DES3_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 DES3_stop_operation(void *state);
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""")
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def adjust_key_parity(key_in):
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"""Set the parity bits in a TDES key.
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:param key_in: the TDES key whose bits need to be adjusted
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:type key_in: byte string
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:returns: a copy of ``key_in``, with the parity bits correctly set
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:rtype: byte string
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:raises ValueError: if the TDES key is not 16 or 24 bytes long
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:raises ValueError: if the TDES key degenerates into Single DES
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"""
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def parity_byte(key_byte):
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parity = 1
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for i in range(1, 8):
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parity ^= (key_byte >> i) & 1
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return (key_byte & 0xFE) | parity
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if len(key_in) not in key_size:
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raise ValueError("Not a valid TDES key")
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key_out = b"".join([ bchr(parity_byte(bord(x))) for x in key_in ])
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if key_out[:8] == key_out[8:16] or key_out[-16:-8] == key_out[-8:]:
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raise ValueError("Triple DES key degenerates to single DES")
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return key_out
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def _create_base_cipher(dict_parameters):
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"""This method instantiates and returns a handle to a low-level base cipher.
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It will absorb named parameters in the process."""
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try:
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key_in = dict_parameters.pop("key")
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except KeyError:
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raise TypeError("Missing 'key' parameter")
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key = adjust_key_parity(bstr(key_in))
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start_operation = _raw_des3_lib.DES3_start_operation
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stop_operation = _raw_des3_lib.DES3_stop_operation
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cipher = VoidPointer()
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result = start_operation(key,
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c_size_t(len(key)),
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cipher.address_of())
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if result:
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raise ValueError("Error %X while instantiating the TDES cipher"
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% result)
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return SmartPointer(cipher.get(), stop_operation)
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def new(key, mode, *args, **kwargs):
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"""Create a new Triple DES cipher.
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:param key:
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The secret key to use in the symmetric cipher.
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It must be 16 or 24 byte long. The parity bits will be ignored.
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:type key: bytes/bytearray/memoryview
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:param mode:
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The chaining mode to use for encryption or decryption.
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:type mode: One of the supported ``MODE_*`` constants
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:Keyword Arguments:
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* **iv** (*bytes*, *bytearray*, *memoryview*) --
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(Only applicable for ``MODE_CBC``, ``MODE_CFB``, ``MODE_OFB``,
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and ``MODE_OPENPGP`` modes).
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The initialization vector to use for encryption or decryption.
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For ``MODE_CBC``, ``MODE_CFB``, and ``MODE_OFB`` it must be 8 bytes long.
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For ``MODE_OPENPGP`` mode only,
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it 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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If not provided, a random byte string is generated (you must then
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read its value with the :attr:`iv` attribute).
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* **nonce** (*bytes*, *bytearray*, *memoryview*) --
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(Only applicable for ``MODE_EAX`` and ``MODE_CTR``).
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A value that must never be reused for any other encryption done
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with this key.
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For ``MODE_EAX`` there are no
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restrictions on its length (recommended: **16** bytes).
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For ``MODE_CTR``, its length must be in the range **[0..7]**.
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If not provided for ``MODE_EAX``, a random byte string is generated (you
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can read it back via the ``nonce`` attribute).
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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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* **mac_len** : (*integer*) --
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(Only ``MODE_EAX``)
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Length of the authentication tag, in bytes.
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It must be no longer than 8 (default).
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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 Triple DES object, of the applicable mode.
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"""
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return _create_cipher(sys.modules[__name__], key, mode, *args, **kwargs)
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MODE_ECB = 1
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MODE_CBC = 2
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MODE_CFB = 3
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MODE_OFB = 5
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MODE_CTR = 6
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MODE_OPENPGP = 7
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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 = (16, 24)
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