#!/usr/bin/env python
#======================================================================
#
# aes_keywrap.py
# --------------
# Python funnctional model of AES Key Wrap including test cases.
# Used to generate test vectors for internal states to drive
# verification of the hardware implementation.
#
#
# Terminology mostly follows the RFC, including variable names.
#
# Block sizes get confusing: AES Key Wrap uses 64-bit blocks, not to
# be confused with AES, which uses 128-bit blocks. In practice, this
# is less confusing than when reading the description, because we
# concatenate two 64-bit blocks just prior to performing an AES ECB
# operation, then immediately split the result back into a pair of
# 64-bit blocks.
#
#
# 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.
#
#======================================================================
from struct import pack, unpack
from os import urandom
from Crypto.Cipher import AES
import unittest
verbose = True
class AESKeyWrapWithPadding(object):
"""
Implementation of AES Key Wrap With Padding from RFC 5649.
using PyCrypto to supply the AES code.
"""
class UnwrapError(Exception):
"Something went wrong during unwrap."
def __init__(self, key):
self.key = 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 bin2hex(bytes, sep = ":"):
return sep.join("{:02x}".format(ord(b)) for b in bytes)
def wrap_key(self, Q):
"""
Wrap a key according to RFC 5649 section 4.1.
Q is the plaintext to be wrapped, a byte string.
Returns C, the wrapped ciphertext.
"""
if verbose:
print("")
print("Performing key wrap.")
print("key: %s" % (self.bin2hex(self.key)))
print("plaintext: %s" % (self.bin2hex(Q)))
print("")
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):
if verbose:
print("Iteration %d, %d" % (j, i))
if verbose:
print("Before encrypt: R[0] = %s R[i] = %s" % (self.bin2hex(R[0]), self.bin2hex(R[i])))
R[0], R[i] = self._encrypt(R[0], R[i])
if verbose:
print("After encrypt: R[0] = %s R[i] = %s" % (self.bin2hex(R[0]), self.bin2hex(R[i])))
W0, W1 = unpack(">LL", R[0])
xorval = n * j + i
W1 ^= xorval
R[0] = pack(">LL", W0, W1)
assert len(R) == (n + 1) and all(len(r) == 8 for r in R)
return "".join(R)
def unwrap_key(self, C):
"""
Unwrap a key according to RFC 5649 section 4.2.
C is the ciphertext to be unwrapped, a byte string
Returns Q, the unwrapped plaintext.
"""
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):
W0, W1 = unpack(">LL", R[0])
W1 ^= n * j + i
R[0] = pack(">LL", W0, W1)
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]
if __name__ == "__main__":
# Test code from here down
class TestAESKeyWrapWithPadding(unittest.TestCase):
@staticmethod
def bin2hex(bytes, sep = ":"):
return sep.join("{:02x}".format(ord(b)) for b in bytes)
@staticmethod
def hex2bin(text):
return text.translate(None, ": \t\n\r").decode("hex")
def loopback_test(self, I):
K = AESKeyWrapWithPadding(self.hex2bin("00:01:02:03:04:05:06:07:08:09:0a:0b:0c:0d:0e:0f"))
C = K.wrap_key(I)
O = K.unwrap_key(C)
self.assertEqual(I, O, "Input and output plaintext did not match: {!r} <> {!r}".format(I, O))
def rfc5649_test(self, K, Q, C):
K = AESKeyWrapWithPadding(key = self.hex2bin(K))
Q = self.hex2bin(Q)
C = self.hex2bin(C)
c = K.wrap_key(Q)
q = K.unwrap_key(C)
self.assertEqual(q, Q, "Input and output plaintext did not match: {} <> {}".format(self.bin2hex(Q), self.bin2hex(q)))
self.assertEqual(c, C, "Input and output ciphertext did not match: {} <> {}".format(self.bin2hex(C), self.bin2hex(c)))
def test_rfc5649_1(self):
self.rfc5649_test(K = "5840df6e29b02af1 ab493b705bf16ea1 ae8338f4dcc176a8",
Q = "c37b7e6492584340 bed1220780894115 5068f738",
C = "138bdeaa9b8fa7fc 61f97742e72248ee 5ae6ae5360d1ae6a 5f54f373fa543b6a")
def test_rfc5649_2(self):
self.rfc5649_test(K = "5840df6e29b02af1 ab493b705bf16ea1 ae8338f4dcc176a8",
Q = "466f7250617369",
C = "afbeb0f07dfbf541 9200f2ccb50bb24f")
def test_mangled_1(self):
self.assertRaises(AESKeyWrapWithPadding.UnwrapError, self.rfc5649_test,
K = "5840df6e29b02af0 ab493b705bf16ea1 ae8338f4dcc176a8",
Q = "466f7250617368",
C = "afbeb0f07dfbf541 9200f2ccb50bb24f")
def test_mangled_2(self):
self.assertRaises(AESKeyWrapWithPadding.UnwrapError, self.rfc5649_test,
K = "5840df6e29b02af0 ab493b705bf16ea1 ae8338f4dcc176a8",
Q = "466f7250617368",
C = "afbeb0f07dfbf541 9200f2ccb50bb24f 0123456789abcdef")
def test_mangled_3(self):
self.assertRaises(AESKeyWrapWithPadding.UnwrapError, self.rfc5649_test,
K = "5840df6e29b02af1 ab493b705bf16ea1 ae8338f4dcc176a8",
Q = "c37b7e6492584340 bed1220780894115 5068f738",
C = "138bdeaa9b8fa7fc 61f97742e72248ee 5ae6ae5360d1ae6a")
# This one should fail. But it doesn't. Que pasa?!?
def test_mangled_4(self):
self.assertRaises(AESKeyWrapWithPadding.UnwrapError, self.rfc5649_test,
K = "5840df6e29b02af1 ab493b705bf16ea1 ae8338f4dcc176a8",
Q = "c37b7e6492584340 bed1220780894115 5068f738",
C = "238bdeaa9b8fa7fc 61f97742e72248ee 5ae6ae5360d1ae6a")
# Test vectors from NISTs set of test vectors for SP800-38F KWP algorithm.
# 128 bit key.
def test_kwp_ae_128_1(self):
self.rfc5649_test(K = "7efb9b3964de316e 7245c86186d98b5f",
Q = "3e",
C = "116a4054c13b7fea de9c22aa57b3caed")
def test_kwp_ae_128_2(self):
self.rfc5649_test(K = "45c770fc26717507 2d70a38269c54685",
Q = "cc5fb15a17795c34",
C = "78ffa3f03b65c55b 812f355730af71ac")
def test_kwp_ae_128_3(self):
self.rfc5649_test(K = "853e2bac0f1e6298 67acea0d2b3c087e",
Q = "49575527bc59530f be",
C = "b43781062eb0317e b2dec6329f2d64de 1c33d85570d57db6")
def test_kwp_ae_128_4(self):
self.rfc5649_test(K = "c03db3cc1416dcd1 c069a195a8d77e3d",
Q = "46f87f58cdda4200 f53d99ce2e49bdb7 6212511fe0cd4d0 b5f37a27d45a288",
C = "57e3b6699c6e8177 59a69492bb7e2cd0 0160d2ebef9bf4d 4eb16fbf798f134 0f6df6558a4fb84cd0")
def test_kwp_ae_256_1(self):
self.rfc5649_test(K = "2800f18237cf8d2b a1dfe361784fd751 9b0fdb0ec73e2ab1 c0b966b9173fc5b5",
Q = "ad",
C = "c1eccf2d077a385e 67aaeb35552c893c")
def test_kwp_ae_256_2(self):
self.rfc5649_test(K = "1c997c2bb5a15a45 93e337b3249675d55 7467417917f6bc51 65c9af6a3e29504",
Q = "3e3eafc50cd4e939",
C = "163eb9e7dbc8ed00 86dffbc6ab00e329")
def test_kwp_ae_256_3(self):
self.rfc5649_test(K = "8df1533f99be6fe6 0f951057fed1daccd 14bd4e34118f24af 677bbf46bf11fe7",
Q = "fb36b1f3907fb5ed ce",
C = "6974d7bae0221b4e d91336c26af77e327 61f6024d8bbf292")
def test_kwp_ae_256_4(self):
self.rfc5649_test(K = "dea4667d911b5c9e c996cdb35da0e29bc 996cbfb0e0a56bac 12fccc334d732eb",
Q = "25d58d437a56a733 2a18541333201f992 9fccde11b06844c1 9ba1ca224cfd6",
C = "86d4e258391f15d7 d4f0ab3e15d6f45e6 5dd2f8caf4c67209 63bb8970fc2f3a4 a58dc74674347ec9")
def test_loopback_1(self):
self.loopback_test("!")
def test_loopback_2(self):
self.loopback_test("Yo!")
def test_loopback_3(self):
self.loopback_test("Hi, Mom")
def test_loopback_4(self):
self.loopback_test("1" * (64 / 8))
def test_loopback_5(self):
self.loopback_test("2" * (128 / 8))
def test_loopback_6(self):
self.loopback_test("3" * (256 / 8))
def test_loopback_7(self):
self.loopback_test("3.14159265358979323846264338327950288419716939937510")
def test_loopback_8(self):
self.loopback_test("3.14159265358979323846264338327950288419716939937510")
def test_loopback_9(self):
self.loopback_test("Hello! My name is Inigo Montoya. You killed my AES key wrapper. Prepare to die.")
def test_joachim_loopback(self):
I = "31:32:33"
K = AESKeyWrapWithPadding(urandom(256/8))
C = K.wrap_key(I)
O = K.unwrap_key(C)
self.assertEqual(I, O, "Input and output plaintext did not match: {!r} <> {!r}".format(I, O))
unittest.main(verbosity = 9)
#======================================================================
# OEF aes_keywrap.py
#======================================================================
