From 33c615feaaf148c099ee4299ad2c8a6f7e1778cf Mon Sep 17 00:00:00 2001 From: Kévin Le Gouguec Date: Sun, 24 Mar 2019 15:19:15 +0100 Subject: [implem-python] Réécriture de certains range() dans tbc.py MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit IME, itérer sur un range() est rarement la façon la plus expressive de faire les choses ; les alternatives imposent une structure qui rendent l'intention plus claire. E.g. quand on voit une compréhension, on comprend que l'auteur cherche à filtrer et/ou transformer ce sur quoi il itère. Réutilisation de xor_state(), renommé xor() puisqu'il sert dans plusieurs situations. Séparation de ce xor() et des fonctions communes aux modes authentifiés pour éviter un import circulaire. --- src/add_python/lilliput/helpers.py | 94 +------------------------------------- 1 file changed, 2 insertions(+), 92 deletions(-) (limited to 'src/add_python/lilliput/helpers.py') diff --git a/src/add_python/lilliput/helpers.py b/src/add_python/lilliput/helpers.py index 65989d0..048aac7 100644 --- a/src/add_python/lilliput/helpers.py +++ b/src/add_python/lilliput/helpers.py @@ -1,92 +1,2 @@ -from .constants import BLOCK_BITS, BLOCK_BYTES -from . import tbc - - -def bytes_to_block_matrix(array): - vector = list(array) - - blocks_nb = len(vector)//BLOCK_BYTES - - block_starts = ( - i*BLOCK_BYTES for i in range(blocks_nb) - ) - - matrix = [ - vector[start:start+BLOCK_BYTES] for start in block_starts - ] - - padding_len = len(vector)%BLOCK_BYTES - - if padding_len > 0: - padding = vector[-padding_len:] - matrix.append(padding) - - return matrix - - -def block_matrix_to_bytes(matrix): - return bytes(byte for block in matrix for byte in block) - - -def xor_state(state1, state2): - return [s1^s2 for (s1, s2) in zip(state1, state2)] - - -def pad10(X): - zeroes = [0] * (BLOCK_BYTES-len(X)-1) - return zeroes + [0b10000000] + X - - -def _tweak_associated_data(t, i, padded): - t_bytes = t//8 - tweak = [0]*(t_bytes) - - mask = 0xff - for byte in range(t_bytes-1): - tweak[byte] = (i & mask) >> (byte * 8) - mask = mask << 8 - - mask = (0xf << (8 * t_bytes-1)) - tweak[-1] = (i & mask) >> ((t_bytes-1)*8) - if not padded: - tweak[-1] |= 0x20 - else: - tweak[-1] |= 0x60 - - return tweak - - -def build_auth(t, A, key): - Auth = [0 for byte in range(0, BLOCK_BYTES)] - l_a = len(A)//BLOCK_BYTES - need_padding = len(A)%BLOCK_BYTES > 0 - - A = bytes_to_block_matrix(A) - - for i in range(0, l_a): - tweak = _tweak_associated_data(t, i, padded=False) - enc = tbc.encrypt(tweak, key, A[i]) - Auth = xor_state(Auth, enc) - - if not need_padding: - return Auth - - tweak = _tweak_associated_data(t, l_a, padded=True) - ad_padded = pad10(A[l_a]) - enc = tbc.encrypt(tweak, key, ad_padded) - Auth = xor_state(Auth, enc) - - return Auth - - -class TagValidationError(Exception): - def __init__(self, announced, computed): - msg = '\n'.join(( - 'Invalid tag:', - announced.hex().upper()+' (announced)', - computed.hex().upper()+' (computed)' - )) - - super().__init__(msg) - self._announced = announced - self._computed = computed +def xor(array1, array2): + return [a1^a2 for (a1, a2) in zip(array1, array2)] -- cgit v1.2.3