393 lines
12 KiB
Python
393 lines
12 KiB
Python
# coding: utf-8
|
|
# PyGOST -- Pure Python GOST cryptographic functions library
|
|
# Copyright (C) 2015-2023 Sergey Matveev <stargrave@stargrave.org>
|
|
#
|
|
# This program is free software: you can redistribute it and/or modify
|
|
# it under the terms of the GNU General Public License as published by
|
|
# the Free Software Foundation, version 3 of the License.
|
|
#
|
|
# This program is distributed in the hope that it will be useful,
|
|
# but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
# GNU General Public License for more details.
|
|
#
|
|
# You should have received a copy of the GNU General Public License
|
|
# along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
"""GOST R 34.13-2015: Modes of operation for block ciphers
|
|
|
|
This module currently includes only padding methods.
|
|
"""
|
|
|
|
from os import urandom
|
|
|
|
from pygost.utils import bytes2long
|
|
from pygost.utils import long2bytes
|
|
from pygost.utils import strxor
|
|
from pygost.utils import xrange
|
|
|
|
|
|
KEYSIZE = 32
|
|
|
|
|
|
def pad_size(data_size, blocksize):
|
|
"""Calculate required pad size to full up blocksize
|
|
"""
|
|
if data_size < blocksize:
|
|
return blocksize - data_size
|
|
if data_size % blocksize == 0:
|
|
return 0
|
|
return blocksize - data_size % blocksize
|
|
|
|
|
|
def pad1(data, blocksize):
|
|
"""Padding method 1
|
|
|
|
Just fill up with zeros if necessary.
|
|
"""
|
|
return data + b"\x00" * pad_size(len(data), blocksize)
|
|
|
|
|
|
def pad2(data, blocksize):
|
|
"""Padding method 2 (also known as ISO/IEC 7816-4)
|
|
|
|
Add one bit and then fill up with zeros.
|
|
"""
|
|
return data + b"\x80" + b"\x00" * pad_size(len(data) + 1, blocksize)
|
|
|
|
|
|
def unpad2(data, blocksize):
|
|
"""Unpad method 2
|
|
"""
|
|
last_block = bytearray(data[-blocksize:])
|
|
pad_index = last_block.rfind(b"\x80")
|
|
if pad_index == -1:
|
|
raise ValueError("Invalid padding")
|
|
for c in last_block[pad_index + 1:]:
|
|
if c != 0:
|
|
raise ValueError("Invalid padding")
|
|
return data[:-(blocksize - pad_index)]
|
|
|
|
|
|
def pad3(data, blocksize):
|
|
"""Padding method 3
|
|
"""
|
|
if pad_size(len(data), blocksize) == 0:
|
|
return data
|
|
return pad2(data, blocksize)
|
|
|
|
|
|
def ecb_encrypt(encrypter, bs, pt):
|
|
"""ECB encryption mode of operation
|
|
|
|
:param encrypter: encrypting function, that takes block as an input
|
|
:param int bs: cipher's blocksize, bytes
|
|
:param bytes pt: already padded plaintext
|
|
"""
|
|
if not pt or len(pt) % bs != 0:
|
|
raise ValueError("Plaintext is not blocksize aligned")
|
|
ct = []
|
|
for i in xrange(0, len(pt), bs):
|
|
ct.append(encrypter(pt[i:i + bs]))
|
|
return b"".join(ct)
|
|
|
|
|
|
def ecb_decrypt(decrypter, bs, ct):
|
|
"""ECB decryption mode of operation
|
|
|
|
:param decrypter: Decrypting function, that takes block as an input
|
|
:param int bs: cipher's blocksize, bytes
|
|
:param bytes ct: ciphertext
|
|
"""
|
|
if not ct or len(ct) % bs != 0:
|
|
raise ValueError("Ciphertext is not blocksize aligned")
|
|
pt = []
|
|
for i in xrange(0, len(ct), bs):
|
|
pt.append(decrypter(ct[i:i + bs]))
|
|
return b"".join(pt)
|
|
|
|
|
|
def acpkm(encrypter, bs):
|
|
"""Perform ACPKM key derivation
|
|
|
|
:param encrypter: encrypting function, that takes block as an input
|
|
:param int bs: cipher's blocksize, bytes
|
|
"""
|
|
return b"".join([
|
|
encrypter(bytes(bytearray(range(d, d + bs))))
|
|
for d in range(0x80, 0x80 + bs * (KEYSIZE // bs), bs)
|
|
])
|
|
|
|
|
|
def ctr(encrypter, bs, data, iv, _acpkm=None):
|
|
"""Counter mode of operation
|
|
|
|
:param encrypter: encrypting function, that takes block as an input
|
|
:param int bs: cipher's blocksize, bytes
|
|
:param bytes data: plaintext/ciphertext
|
|
:param bytes iv: half blocksize-sized initialization vector
|
|
|
|
For decryption you use the same function again.
|
|
"""
|
|
if len(iv) != bs // 2:
|
|
raise ValueError("Invalid IV size")
|
|
if len(data) > bs * (1 << (8 * (bs // 2 - 1))):
|
|
raise ValueError("Too big data")
|
|
stream = []
|
|
ctr_value = 0
|
|
ctr_max_value = 1 << (8 * (bs // 2))
|
|
if _acpkm is not None:
|
|
acpkm_algo_class, acpkm_section_size_in_bs = _acpkm
|
|
acpkm_section_size_in_bs //= bs
|
|
for _ in xrange(0, len(data) + pad_size(len(data), bs), bs):
|
|
if (
|
|
_acpkm is not None and
|
|
ctr_value != 0 and
|
|
ctr_value % acpkm_section_size_in_bs == 0
|
|
):
|
|
encrypter = acpkm_algo_class(acpkm(encrypter, bs)).encrypt
|
|
stream.append(encrypter(iv + long2bytes(ctr_value, bs // 2)))
|
|
ctr_value = (ctr_value + 1) % ctr_max_value
|
|
return strxor(b"".join(stream), data)
|
|
|
|
|
|
def ctr_acpkm(algo_class, encrypter, section_size, bs, data, iv):
|
|
"""CTR-ACPKM mode of operation
|
|
|
|
:param algo_class: pygost.gost3412's algorithm class
|
|
:param encrypter: encrypting function, that takes block as an input
|
|
:param int section_size: ACPKM'es section size (N), in bytes
|
|
:param int bs: cipher's blocksize, bytes
|
|
:param bytes data: plaintext/ciphertext
|
|
:param bytes iv: half blocksize-sized initialization vector
|
|
|
|
For decryption you use the same function again.
|
|
"""
|
|
if section_size % bs != 0:
|
|
raise ValueError("section_size must be multiple of bs")
|
|
return ctr(encrypter, bs, data, iv, _acpkm=(algo_class, section_size))
|
|
|
|
|
|
def ofb(encrypter, bs, data, iv):
|
|
"""OFB mode of operation
|
|
|
|
:param encrypter: encrypting function, that takes block as an input
|
|
:param int bs: cipher's blocksize, bytes
|
|
:param bytes data: plaintext/ciphertext
|
|
:param bytes iv: blocksize-sized initialization vector
|
|
|
|
For decryption you use the same function again.
|
|
"""
|
|
if len(iv) < bs or len(iv) % bs != 0:
|
|
raise ValueError("Invalid IV size")
|
|
r = [iv[i:i + bs] for i in range(0, len(iv), bs)]
|
|
result = []
|
|
for i in xrange(0, len(data) + pad_size(len(data), bs), bs):
|
|
r = r[1:] + [encrypter(r[0])]
|
|
result.append(strxor(r[-1], data[i:i + bs]))
|
|
return b"".join(result)
|
|
|
|
|
|
def cbc_encrypt(encrypter, bs, pt, iv):
|
|
"""CBC encryption mode of operation
|
|
|
|
:param encrypter: encrypting function, that takes block as an input
|
|
:param int bs: cipher's blocksize, bytes
|
|
:param bytes pt: already padded plaintext
|
|
:param bytes iv: blocksize-sized initialization vector
|
|
"""
|
|
if not pt or len(pt) % bs != 0:
|
|
raise ValueError("Plaintext is not blocksize aligned")
|
|
if len(iv) < bs or len(iv) % bs != 0:
|
|
raise ValueError("Invalid IV size")
|
|
r = [iv[i:i + bs] for i in range(0, len(iv), bs)]
|
|
ct = []
|
|
for i in xrange(0, len(pt), bs):
|
|
ct.append(encrypter(strxor(r[0], pt[i:i + bs])))
|
|
r = r[1:] + [ct[-1]]
|
|
return b"".join(ct)
|
|
|
|
|
|
def cbc_decrypt(decrypter, bs, ct, iv):
|
|
"""CBC decryption mode of operation
|
|
|
|
:param decrypter: Decrypting function, that takes block as an input
|
|
:param int bs: cipher's blocksize, bytes
|
|
:param bytes ct: ciphertext
|
|
:param bytes iv: blocksize-sized initialization vector
|
|
"""
|
|
if not ct or len(ct) % bs != 0:
|
|
raise ValueError("Ciphertext is not blocksize aligned")
|
|
if len(iv) < bs or len(iv) % bs != 0:
|
|
raise ValueError("Invalid IV size")
|
|
r = [iv[i:i + bs] for i in range(0, len(iv), bs)]
|
|
pt = []
|
|
for i in xrange(0, len(ct), bs):
|
|
blk = ct[i:i + bs]
|
|
pt.append(strxor(r[0], decrypter(blk)))
|
|
r = r[1:] + [blk]
|
|
return b"".join(pt)
|
|
|
|
|
|
def cfb_encrypt(encrypter, bs, pt, iv):
|
|
"""CFB encryption mode of operation
|
|
|
|
:param encrypter: encrypting function, that takes block as an input
|
|
:param int bs: cipher's blocksize, bytes
|
|
:param bytes pt: plaintext
|
|
:param bytes iv: blocksize-sized initialization vector
|
|
"""
|
|
if len(iv) < bs or len(iv) % bs != 0:
|
|
raise ValueError("Invalid IV size")
|
|
r = [iv[i:i + bs] for i in range(0, len(iv), bs)]
|
|
ct = []
|
|
for i in xrange(0, len(pt) + pad_size(len(pt), bs), bs):
|
|
ct.append(strxor(encrypter(r[0]), pt[i:i + bs]))
|
|
r = r[1:] + [ct[-1]]
|
|
return b"".join(ct)
|
|
|
|
|
|
def cfb_decrypt(encrypter, bs, ct, iv):
|
|
"""CFB decryption mode of operation
|
|
|
|
:param encrypter: encrypting function, that takes block as an input
|
|
:param int bs: cipher's blocksize, bytes
|
|
:param bytes ct: ciphertext
|
|
:param bytes iv: blocksize-sized initialization vector
|
|
"""
|
|
if len(iv) < bs or len(iv) % bs != 0:
|
|
raise ValueError("Invalid IV size")
|
|
r = [iv[i:i + bs] for i in range(0, len(iv), bs)]
|
|
pt = []
|
|
for i in xrange(0, len(ct) + pad_size(len(ct), bs), bs):
|
|
blk = ct[i:i + bs]
|
|
pt.append(strxor(encrypter(r[0]), blk))
|
|
r = r[1:] + [blk]
|
|
return b"".join(pt)
|
|
|
|
|
|
def _mac_shift(bs, data, xor_lsb=0):
|
|
num = (bytes2long(data) << 1) ^ xor_lsb
|
|
return long2bytes(num, bs)[-bs:]
|
|
|
|
|
|
Rb64 = 0b11011
|
|
Rb128 = 0b10000111
|
|
|
|
|
|
def _mac_ks(encrypter, bs):
|
|
Rb = Rb128 if bs == 16 else Rb64
|
|
_l = encrypter(bs * b"\x00")
|
|
k1 = _mac_shift(bs, _l, Rb) if bytearray(_l)[0] & 0x80 > 0 else _mac_shift(bs, _l)
|
|
k2 = _mac_shift(bs, k1, Rb) if bytearray(k1)[0] & 0x80 > 0 else _mac_shift(bs, k1)
|
|
return k1, k2
|
|
|
|
|
|
def mac(encrypter, bs, data):
|
|
"""MAC (known here as CMAC, OMAC1) mode of operation
|
|
|
|
:param encrypter: encrypting function, that takes block as an input
|
|
:param int bs: cipher's blocksize, bytes
|
|
:param bytes data: data to authenticate
|
|
|
|
Implementation is based on PyCrypto's CMAC one, that is in public domain.
|
|
"""
|
|
k1, k2 = _mac_ks(encrypter, bs)
|
|
if len(data) % bs == 0:
|
|
tail_offset = len(data) - bs
|
|
else:
|
|
tail_offset = len(data) - (len(data) % bs)
|
|
prev = bs * b"\x00"
|
|
for i in xrange(0, tail_offset, bs):
|
|
prev = encrypter(strxor(data[i:i + bs], prev))
|
|
tail = data[tail_offset:]
|
|
return encrypter(strxor(
|
|
strxor(pad3(tail, bs), prev),
|
|
k1 if len(tail) == bs else k2,
|
|
))
|
|
|
|
|
|
def acpkm_master(algo_class, encrypter, key_section_size, bs, keymat_len):
|
|
"""ACPKM-Master key derivation
|
|
|
|
:param algo_class: pygost.gost3412's algorithm class
|
|
:param encrypter: encrypting function, that takes block as an input
|
|
:param int key_section_size: ACPKM'es key section size (T*), in bytes
|
|
:param int bs: cipher's blocksize, bytes
|
|
:param int keymat_len: length of key material to produce
|
|
"""
|
|
return ctr_acpkm(
|
|
algo_class,
|
|
encrypter,
|
|
key_section_size,
|
|
bs,
|
|
data=b"\x00" * keymat_len,
|
|
iv=b"\xFF" * (bs // 2),
|
|
)
|
|
|
|
|
|
def mac_acpkm_master(algo_class, encrypter, key_section_size, section_size, bs, data):
|
|
"""OMAC-ACPKM-Master
|
|
|
|
:param algo_class: pygost.gost3412's algorithm class
|
|
:param encrypter: encrypting function, that takes block as an input
|
|
:param int key_section_size: ACPKM'es key section size (T*), in bytes
|
|
:param int section_size: ACPKM'es section size (N), in bytes
|
|
:param int bs: cipher's blocksize, bytes
|
|
:param bytes data: data to authenticate
|
|
"""
|
|
if len(data) % bs == 0:
|
|
tail_offset = len(data) - bs
|
|
else:
|
|
tail_offset = len(data) - (len(data) % bs)
|
|
prev = bs * b"\x00"
|
|
sections = len(data) // section_size
|
|
if len(data) % section_size != 0:
|
|
sections += 1
|
|
keymats = acpkm_master(
|
|
algo_class,
|
|
encrypter,
|
|
key_section_size,
|
|
bs,
|
|
(KEYSIZE + bs) * sections,
|
|
)
|
|
for i in xrange(0, tail_offset, bs):
|
|
if i % section_size == 0:
|
|
keymat, keymats = keymats[:KEYSIZE + bs], keymats[KEYSIZE + bs:]
|
|
key, k1 = keymat[:KEYSIZE], keymat[KEYSIZE:]
|
|
encrypter = algo_class(key).encrypt
|
|
prev = encrypter(strxor(data[i:i + bs], prev))
|
|
tail = data[tail_offset:]
|
|
if len(tail) == bs:
|
|
key, k1 = keymats[:KEYSIZE], keymats[KEYSIZE:]
|
|
encrypter = algo_class(key).encrypt
|
|
k2 = long2bytes(bytes2long(k1) << 1, size=bs)
|
|
if bytearray(k1)[0] & 0x80 != 0:
|
|
k2 = strxor(k2, long2bytes(Rb128 if bs == 16 else Rb64, size=bs))
|
|
return encrypter(strxor(
|
|
strxor(pad3(tail, bs), prev),
|
|
k1 if len(tail) == bs else k2,
|
|
))
|
|
|
|
|
|
def pad_iso10126(data, blocksize):
|
|
"""ISO 10126 padding
|
|
|
|
Does not exist in 34.13, but added for convenience.
|
|
It uses urandom call for getting the randomness.
|
|
"""
|
|
pad_len = blocksize - len(data) % blocksize
|
|
if pad_len == 0:
|
|
pad_len = blocksize
|
|
return b"".join((data, urandom(pad_len - 1), bytes((pad_len,))))
|
|
|
|
|
|
def unpad_iso10126(data, blocksize):
|
|
"""Unpad :py:func:`pygost.gost3413.pad_iso10126`
|
|
"""
|
|
if len(data) % blocksize != 0:
|
|
raise ValueError("Data length is not multiple of blocksize")
|
|
pad_len = bytearray(data)[-1]
|
|
if pad_len > blocksize:
|
|
raise ValueError("Padding length is bigger than blocksize")
|
|
return data[:-pad_len]
|