X-Git-Url: http://www.git.cypherpunks.ru/?a=blobdiff_plain;f=pygost%2Fgost3413.py;h=3a539d2e4b1f9097e78774ea3cf263df648a9d5a;hb=54735617392b3988c2e24b59e0c552d74736e320;hp=5fb73f8ccf9d30d12830d2626b1229d4f004de1f;hpb=c5a63fc144c59342e32304e4e86b2bad479a8187;p=pygost.git

diff --git a/pygost/gost3413.py b/pygost/gost3413.py
index 5fb73f8..3a539d2 100644
--- a/pygost/gost3413.py
+++ b/pygost/gost3413.py
@@ -1,11 +1,10 @@
 # coding: utf-8
 # PyGOST -- Pure Python GOST cryptographic functions library
-# Copyright (C) 2015-2016 Sergey Matveev <stargrave@stargrave.org>
+# Copyright (C) 2015-2020 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, either version 3 of the License, or
-# (at your option) any later version.
+# 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
@@ -19,9 +18,14 @@
 This module currently includes only padding methods.
 """
 
+from pygost.utils import bytes2long
+from pygost.utils import long2bytes
+from pygost.utils import strxor
+from pygost.utils import xrange
+
 
 def pad_size(data_size, blocksize):
-    """Calculate required pad size to full up BLOCKSIZE
+    """Calculate required pad size to full up blocksize
     """
     if data_size < blocksize:
         return blocksize - data_size
@@ -46,9 +50,207 @@ def pad2(data, blocksize):
     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
+    :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
+    :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 ctr(encrypter, bs, data, iv):
+    """Counter mode of operation
+
+    :param encrypter: encrypting function, that takes block as an input
+    :param int bs: cipher's blocksize
+    :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")
+    stream = []
+    ctr_value = 0
+    for _ in xrange(0, len(data) + pad_size(len(data), bs), bs):
+        stream.append(encrypter(iv + long2bytes(ctr_value, bs // 2)))
+        ctr_value += 1
+    return strxor(b"".join(stream), data)
+
+
+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
+    :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
+    :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
+    :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
+    :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
+    :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:]
+
+
+def _mac_ks(encrypter, bs):
+    Rb = 0b10000111 if bs == 16 else 0b11011
+    _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
+    :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,
+    ))