1  #!/usr/bin/env python3
  2  # Copyright (c) 2022-present The Bitcoin Core developers
  3  # Distributed under the MIT software license, see the accompanying
  4  # file COPYING or http://www.opensource.org/licenses/mit-license.php.
  5  
  6  """Test-only implementation of Poly1305 authenticator
  7  
  8  It is designed for ease of understanding, not performance.
  9  
 10  WARNING: This code is slow and trivially vulnerable to side channel attacks. Do not use for
 11  anything but tests.
 12  """
 13  
 14  import unittest
 15  
 16  
 17  class Poly1305:
 18      """Class representing a running poly1305 computation."""
 19      MODULUS = 2**130 - 5
 20  
 21      def __init__(self, key):
 22          self.r = int.from_bytes(key[:16], 'little') & 0xffffffc0ffffffc0ffffffc0fffffff
 23          self.s = int.from_bytes(key[16:], 'little')
 24  
 25      def tag(self, data):
 26          """Compute the poly1305 tag."""
 27          acc, length = 0, len(data)
 28          for i in range((length + 15) // 16):
 29              chunk = data[i * 16:min(length, (i + 1) * 16)]
 30              val = int.from_bytes(chunk, 'little') + 256**len(chunk)
 31              acc = (self.r * (acc + val)) % Poly1305.MODULUS
 32          return ((acc + self.s) & 0xffffffffffffffffffffffffffffffff).to_bytes(16, 'little')
 33  
 34  
 35  # Test vectors from RFC7539/8439 consisting of message to be authenticated, 32 byte key and computed 16 byte tag
 36  POLY1305_TESTS = [
 37      # RFC 7539, section 2.5.2.
 38      ["43727970746f6772617068696320466f72756d2052657365617263682047726f7570",
 39       "85d6be7857556d337f4452fe42d506a80103808afb0db2fd4abff6af4149f51b",
 40       "a8061dc1305136c6c22b8baf0c0127a9"],
 41      # RFC 7539, section A.3.
 42      ["00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
 43       "000000000000000000000000000",
 44       "0000000000000000000000000000000000000000000000000000000000000000",
 45       "00000000000000000000000000000000"],
 46      ["416e79207375626d697373696f6e20746f20746865204945544620696e74656e6465642062792074686520436f6e747269627"
 47       "5746f7220666f72207075626c69636174696f6e20617320616c6c206f722070617274206f6620616e204945544620496e7465"
 48       "726e65742d4472616674206f722052464320616e6420616e792073746174656d656e74206d6164652077697468696e2074686"
 49       "520636f6e74657874206f6620616e204945544620616374697669747920697320636f6e7369646572656420616e2022494554"
 50       "4620436f6e747269627574696f6e222e20537563682073746174656d656e747320696e636c756465206f72616c20737461746"
 51       "56d656e747320696e20494554462073657373696f6e732c2061732077656c6c206173207772697474656e20616e6420656c65"
 52       "6374726f6e696320636f6d6d756e69636174696f6e73206d61646520617420616e792074696d65206f7220706c6163652c207"
 53       "768696368206172652061646472657373656420746f",
 54       "0000000000000000000000000000000036e5f6b5c5e06070f0efca96227a863e",
 55       "36e5f6b5c5e06070f0efca96227a863e"],
 56      ["416e79207375626d697373696f6e20746f20746865204945544620696e74656e6465642062792074686520436f6e747269627"
 57       "5746f7220666f72207075626c69636174696f6e20617320616c6c206f722070617274206f6620616e204945544620496e7465"
 58       "726e65742d4472616674206f722052464320616e6420616e792073746174656d656e74206d6164652077697468696e2074686"
 59       "520636f6e74657874206f6620616e204945544620616374697669747920697320636f6e7369646572656420616e2022494554"
 60       "4620436f6e747269627574696f6e222e20537563682073746174656d656e747320696e636c756465206f72616c20737461746"
 61       "56d656e747320696e20494554462073657373696f6e732c2061732077656c6c206173207772697474656e20616e6420656c65"
 62       "6374726f6e696320636f6d6d756e69636174696f6e73206d61646520617420616e792074696d65206f7220706c6163652c207"
 63       "768696368206172652061646472657373656420746f",
 64       "36e5f6b5c5e06070f0efca96227a863e00000000000000000000000000000000",
 65       "f3477e7cd95417af89a6b8794c310cf0"],
 66      ["2754776173206272696c6c69672c20616e642074686520736c6974687920746f7665730a446964206779726520616e6420676"
 67       "96d626c6520696e2074686520776162653a0a416c6c206d696d737920776572652074686520626f726f676f7665732c0a416e"
 68       "6420746865206d6f6d65207261746873206f757467726162652e",
 69       "1c9240a5eb55d38af333888604f6b5f0473917c1402b80099dca5cbc207075c0",
 70       "4541669a7eaaee61e708dc7cbcc5eb62"],
 71      ["ffffffffffffffffffffffffffffffff",
 72       "0200000000000000000000000000000000000000000000000000000000000000",
 73       "03000000000000000000000000000000"],
 74      ["02000000000000000000000000000000",
 75       "02000000000000000000000000000000ffffffffffffffffffffffffffffffff",
 76       "03000000000000000000000000000000"],
 77      ["fffffffffffffffffffffffffffffffff0ffffffffffffffffffffffffffffff11000000000000000000000000000000",
 78       "0100000000000000000000000000000000000000000000000000000000000000",
 79       "05000000000000000000000000000000"],
 80      ["fffffffffffffffffffffffffffffffffbfefefefefefefefefefefefefefefe01010101010101010101010101010101",
 81       "0100000000000000000000000000000000000000000000000000000000000000",
 82       "00000000000000000000000000000000"],
 83      ["fdffffffffffffffffffffffffffffff",
 84       "0200000000000000000000000000000000000000000000000000000000000000",
 85       "faffffffffffffffffffffffffffffff"],
 86      ["e33594d7505e43b900000000000000003394d7505e4379cd01000000000000000000000000000000000000000000000001000000000000000000000000000000",
 87       "0100000000000000040000000000000000000000000000000000000000000000",
 88       "14000000000000005500000000000000"],
 89      ["e33594d7505e43b900000000000000003394d7505e4379cd010000000000000000000000000000000000000000000000",
 90       "0100000000000000040000000000000000000000000000000000000000000000",
 91       "13000000000000000000000000000000"],
 92  ]
 93  
 94  
 95  class TestFrameworkPoly1305(unittest.TestCase):
 96      def test_poly1305(self):
 97          """Poly1305 test vectors."""
 98          for test_vector in POLY1305_TESTS:
 99              hex_message, hex_key, hex_tag = test_vector
100              message = bytes.fromhex(hex_message)
101              key = bytes.fromhex(hex_key)
102              tag = bytes.fromhex(hex_tag)
103              comp_tag = Poly1305(key).tag(message)
104              self.assertEqual(tag, comp_tag)