#!/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 #======================================================================