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| from binascii import unhexlify
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|
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| from Cryptodome.Util.py3compat import bord, tobytes, _copy_bytes
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|
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| from Cryptodome.Hash import BLAKE2s
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| from Cryptodome.Random import get_random_bytes
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| from Cryptodome.Util._raw_api import (load_pycryptodome_raw_lib,
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| VoidPointer, SmartPointer,
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| create_string_buffer,
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| get_raw_buffer, c_size_t,
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| c_uint8_ptr)
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|
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| _raw_poly1305 = load_pycryptodome_raw_lib("Cryptodome.Hash._poly1305",
|
| """
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| int poly1305_init(void **state,
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| const uint8_t *r,
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| size_t r_len,
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| const uint8_t *s,
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| size_t s_len);
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| int poly1305_destroy(void *state);
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| int poly1305_update(void *state,
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| const uint8_t *in,
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| size_t len);
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| int poly1305_digest(const void *state,
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| uint8_t *digest,
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| size_t len);
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| """)
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|
|
|
|
| class Poly1305_MAC(object):
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| """An Poly1305 MAC object.
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| Do not instantiate directly. Use the :func:`new` function.
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|
|
| :ivar digest_size: the size in bytes of the resulting MAC tag
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| :vartype digest_size: integer
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| """
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|
|
| digest_size = 16
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|
|
| def __init__(self, r, s, data):
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|
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| if len(r) != 16:
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| raise ValueError("Parameter r is not 16 bytes long")
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| if len(s) != 16:
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| raise ValueError("Parameter s is not 16 bytes long")
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|
|
| self._mac_tag = None
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|
|
| state = VoidPointer()
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| result = _raw_poly1305.poly1305_init(state.address_of(),
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| c_uint8_ptr(r),
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| c_size_t(len(r)),
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| c_uint8_ptr(s),
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| c_size_t(len(s))
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| )
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| if result:
|
| raise ValueError("Error %d while instantiating Poly1305" % result)
|
| self._state = SmartPointer(state.get(),
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| _raw_poly1305.poly1305_destroy)
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| if data:
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| self.update(data)
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|
|
| def update(self, data):
|
| """Authenticate the next chunk of message.
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|
|
| Args:
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| data (byte string/byte array/memoryview): The next chunk of data
|
| """
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|
|
| if self._mac_tag:
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| raise TypeError("You can only call 'digest' or 'hexdigest' on this object")
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|
|
| result = _raw_poly1305.poly1305_update(self._state.get(),
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| c_uint8_ptr(data),
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| c_size_t(len(data)))
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| if result:
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| raise ValueError("Error %d while hashing Poly1305 data" % result)
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| return self
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|
|
| def copy(self):
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| raise NotImplementedError()
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|
|
| def digest(self):
|
| """Return the **binary** (non-printable) MAC tag of the message
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| authenticated so far.
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|
|
| :return: The MAC tag digest, computed over the data processed so far.
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| Binary form.
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| :rtype: byte string
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| """
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|
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| if self._mac_tag:
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| return self._mac_tag
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|
|
| bfr = create_string_buffer(16)
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| result = _raw_poly1305.poly1305_digest(self._state.get(),
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| bfr,
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| c_size_t(len(bfr)))
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| if result:
|
| raise ValueError("Error %d while creating Poly1305 digest" % result)
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|
|
| self._mac_tag = get_raw_buffer(bfr)
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| return self._mac_tag
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|
|
| def hexdigest(self):
|
| """Return the **printable** MAC tag of the message authenticated so far.
|
|
|
| :return: The MAC tag, computed over the data processed so far.
|
| Hexadecimal encoded.
|
| :rtype: string
|
| """
|
|
|
| return "".join(["%02x" % bord(x)
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| for x in tuple(self.digest())])
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|
|
| def verify(self, mac_tag):
|
| """Verify that a given **binary** MAC (computed by another party)
|
| is valid.
|
|
|
| Args:
|
| mac_tag (byte string/byte string/memoryview): the expected MAC of the message.
|
|
|
| Raises:
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| ValueError: if the MAC does not match. It means that the message
|
| has been tampered with or that the MAC key is incorrect.
|
| """
|
|
|
| secret = get_random_bytes(16)
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|
|
| mac1 = BLAKE2s.new(digest_bits=160, key=secret, data=mac_tag)
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| mac2 = BLAKE2s.new(digest_bits=160, key=secret, data=self.digest())
|
|
|
| if mac1.digest() != mac2.digest():
|
| raise ValueError("MAC check failed")
|
|
|
| def hexverify(self, hex_mac_tag):
|
| """Verify that a given **printable** MAC (computed by another party)
|
| is valid.
|
|
|
| Args:
|
| hex_mac_tag (string): the expected MAC of the message,
|
| as a hexadecimal string.
|
|
|
| Raises:
|
| ValueError: if the MAC does not match. It means that the message
|
| has been tampered with or that the MAC key is incorrect.
|
| """
|
|
|
| self.verify(unhexlify(tobytes(hex_mac_tag)))
|
|
|
|
|
|
|
| def new(**kwargs):
|
| """Create a new Poly1305 MAC object.
|
|
|
| Args:
|
| key (bytes/bytearray/memoryview):
|
| The 32-byte key for the Poly1305 object.
|
| cipher (module from ``Cryptodome.Cipher``):
|
| The cipher algorithm to use for deriving the Poly1305
|
| key pair *(r, s)*.
|
| It can only be ``Cryptodome.Cipher.AES`` or ``Cryptodome.Cipher.ChaCha20``.
|
| nonce (bytes/bytearray/memoryview):
|
| Optional. The non-repeatable value to use for the MAC of this message.
|
| It must be 16 bytes long for ``AES`` and 8 or 12 bytes for ``ChaCha20``.
|
| If not passed, a random nonce is created; you will find it in the
|
| ``nonce`` attribute of the new object.
|
| data (bytes/bytearray/memoryview):
|
| Optional. The very first chunk of the message to authenticate.
|
| It is equivalent to an early call to ``update()``.
|
|
|
| Returns:
|
| A :class:`Poly1305_MAC` object
|
| """
|
|
|
| cipher = kwargs.pop("cipher", None)
|
| if not hasattr(cipher, '_derive_Poly1305_key_pair'):
|
| raise ValueError("Parameter 'cipher' must be AES or ChaCha20")
|
|
|
| cipher_key = kwargs.pop("key", None)
|
| if cipher_key is None:
|
| raise TypeError("You must pass a parameter 'key'")
|
|
|
| nonce = kwargs.pop("nonce", None)
|
| data = kwargs.pop("data", None)
|
|
|
| if kwargs:
|
| raise TypeError("Unknown parameters: " + str(kwargs))
|
|
|
| r, s, nonce = cipher._derive_Poly1305_key_pair(cipher_key, nonce)
|
|
|
| new_mac = Poly1305_MAC(r, s, data)
|
| new_mac.nonce = _copy_bytes(None, None, nonce)
|
| return new_mac
|
|
|
