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-#!/usr/bin/env python
-# -*- coding: utf-8 -*-
-#=======================================================================
-#
-# keywrap.py
-# ----------
-# Python model to test AES KEY WRAP according to RFC 5649.
-#
-#
-# Author: Joachim Strombergson, Rob Austein
-# Copyright (c) 2018, NORDUnet A/S
-# All rights reserved.
-#
-# Redistribution and use in source and binary forms, with or without
-# modification, are permitted provided that the following conditions are
-# met:
-# - Redistributions of source code must retain the above copyright notice,
-# this list of conditions and the following disclaimer.
-#
-# - Redistributions in binary form must reproduce the above copyright
-# notice, this list of conditions and the following disclaimer in the
-# documentation and/or other materials provided with the distribution.
-#
-# - Neither the name of the NORDUnet nor the names of its contributors may
-# be used to endorse or promote products derived from this software
-# without specific prior written permission.
-#
-# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
-# IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
-# TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
-# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-# HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
-# TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
-# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
-# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
-# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
-# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-#
-#=======================================================================
-
-#-------------------------------------------------------------------
-# Python module imports.
-#-------------------------------------------------------------------
-import sys
-import Crypto.Random
-from Crypto.Cipher import AES
-from struct import pack, unpack
-
-
-#-------------------------------------------------------------------
-# Constants.
-#-------------------------------------------------------------------
-VERBOSE = True
-
-
-
-#-------------------------------------------------------------------
-# AESKeyWrapWithPadding
-#-------------------------------------------------------------------
-class AESKeyWrapWithPadding(object):
- """
- Implementation of AES Key Wrap With Padding from RFC 5649.
- """
-
- class UnwrapError(Exception):
- "Something went wrong during unwrap."
-
- def __init__(self, key):
- self.ctx = AES.new(key, AES.MODE_ECB)
-
- def _encrypt(self, b1, b2):
- aes_block = self.ctx.encrypt(b1 + b2)
- return aes_block[:8], aes_block[8:]
-
- def _decrypt(self, b1, b2):
- aes_block = self.ctx.decrypt(b1 + b2)
- return aes_block[:8], aes_block[8:]
-
- @staticmethod
- def _start_stop(start, stop): # Syntactic sugar
- step = -1 if start > stop else 1
- return xrange(start, stop + step, step)
-
- @staticmethod
- def _xor(R0, t):
- return pack(">Q", unpack(">Q", R0)[0] ^ t)
-
- def wrap(self, Q):
- "RFC 5649 section 4.1."
- m = len(Q) # Plaintext length
- if m % 8 != 0: # Pad Q if needed
- Q += "\x00" * (8 - (m % 8))
- R = [pack(">LL", 0xa65959a6, m)] # Magic MSB(32,A), build LSB(32,A)
- R.extend(Q[i : i + 8] # Append Q
- for i in xrange(0, len(Q), 8))
- n = len(R) - 1
- if n == 1:
- R[0], R[1] = self._encrypt(R[0], R[1])
- else:
- # RFC 3394 section 2.2.1
- for j in self._start_stop(0, 5):
- for i in self._start_stop(1, n):
- R[0], R[i] = self._encrypt(R[0], R[i])
- R[0] = self._xor(R[0], n * j + i)
- assert len(R) == (n + 1) and all(len(r) == 8 for r in R)
- return "".join(R)
-
- def unwrap(self, C):
- "RFC 5649 section 4.2."
- if len(C) % 8 != 0:
- raise self.UnwrapError("Ciphertext length {} is not an integral number of blocks"
- .format(len(C)))
- n = (len(C) / 8) - 1
- R = [C[i : i + 8] for i in xrange(0, len(C), 8)]
- if n == 1:
- R[0], R[1] = self._decrypt(R[0], R[1])
- else:
- # RFC 3394 section 2.2.2 steps (1), (2), and part of (3)
- for j in self._start_stop(5, 0):
- for i in self._start_stop(n, 1):
- R[0] = self._xor(R[0], n * j + i)
- R[0], R[i] = self._decrypt(R[0], R[i])
- magic, m = unpack(">LL", R[0])
- if magic != 0xa65959a6:
- raise self.UnwrapError("Magic value in AIV should have been 0xa65959a6, was 0x{:02x}"
- .format(magic))
- if m <= 8 * (n - 1) or m > 8 * n:
- raise self.UnwrapError("Length encoded in AIV out of range: m {}, n {}".format(m, n))
- R = "".join(R[1:])
- assert len(R) == 8 * n
- if any(r != "\x00" for r in R[m:]):
- raise self.UnwrapError("Nonzero trailing bytes {}".format(R[m:].encode("hex")))
- return R[:m]
-
-
-#-------------------------------------------------------------------
-# wrap_test1
-#
-# First, simplest test from NIST test vectors.
-#-------------------------------------------------------------------
-def wrap_test1():
- my_key = Crypto.Random.new().read(256/8)
- my_keywrap = AESKeyWrapWithPadding(my_key)
-
- my_plaintext = "\x31\x32\x33"
- my_wrap = my_keywrap.wrap(my_plaintext)
- print(type(my_wrap))
- my_unwrap = my_keywrap.wrap(my_wrap)
- print(type(my_unwrap))
- print("plaintext: %s wrapped: %s unwrapped: %s" %
- (my_plaintext, my_wrap, my_unwrap))
-
-
-#-------------------------------------------------------------------
-#-------------------------------------------------------------------
-def main():
- print("Testing the Key Wrap Python model")
- print("=================================")
- print
- # keywrap_aes_test()
- wrap_test1()
-
-
-#-------------------------------------------------------------------
-# __name__
-# Python thingy which allows the file to be run standalone as
-# well as parsed from within a Python interpreter.
-#-------------------------------------------------------------------
-if __name__=="__main__":
- # Run the main function.
- sys.exit(main())
-
-#=======================================================================
-# EOF keywrap.py
-#=======================================================================