# # Hash/Poly1305.py - Implements the Poly1305 MAC # # =================================================================== # The contents of this file are dedicated to the public domain. To # the extent that dedication to the public domain is not available, # everyone is granted a worldwide, perpetual, royalty-free, # non-exclusive license to exercise all rights associated with the # contents of this file for any purpose whatsoever. # No rights are reserved. # # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, # EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND # NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS # BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN # ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE # SOFTWARE. # =================================================================== from __future__ import annotations from binascii import unhexlify from hmac import compare_digest from typing import TYPE_CHECKING, Optional, Union from Crypto.Util._bytes import tobytes from Crypto.Util._raw_api import ( SmartPointer, VoidPointer, c_size_t, c_uint8_ptr_len, create_string_buffer, get_raw_buffer, load_pycryptodome_raw_lib, ) if TYPE_CHECKING: from types import ModuleType Buffer = Union[bytes, bytearray, memoryview] _raw_poly1305 = load_pycryptodome_raw_lib( "Crypto.Hash._poly1305", """ int poly1305_init(void **state, const uint8_t *r, size_t r_len, const uint8_t *s, size_t s_len); int poly1305_destroy(void *state); int poly1305_update(void *state, const uint8_t *in, size_t len); int poly1305_digest(const void *state, uint8_t *digest, size_t len); """, ) class Poly1305_MAC: """An Poly1305 MAC object. Do not instantiate directly. Use the :func:`new` function. :ivar digest_size: the size in bytes of the resulting MAC tag :vartype digest_size: integer """ digest_size: int = 16 nonce: bytes def __init__(self, r: bytes, s: bytes, data: Optional[Buffer]) -> None: if len(r) != 16: raise ValueError("Parameter r is not 16 bytes long") if len(s) != 16: raise ValueError("Parameter s is not 16 bytes long") self._mac_tag: Optional[bytes] = None state = VoidPointer() r_ptr, r_len = c_uint8_ptr_len(r) s_ptr, s_len = c_uint8_ptr_len(s) result = _raw_poly1305.poly1305_init( state.address_of(), r_ptr, c_size_t(r_len), s_ptr, c_size_t(s_len) ) if result: raise ValueError("Error %d while instantiating Poly1305" % result) self._state = SmartPointer(state.get(), _raw_poly1305.poly1305_destroy) if data: self.update(data) def update(self, data: Buffer) -> Poly1305_MAC: """Authenticate the next chunk of message. Args: data (byte string/byte array/memoryview): The next chunk of data """ if self._mac_tag: raise TypeError("You can only call 'digest' or 'hexdigest' on this object") data_ptr, data_len = c_uint8_ptr_len(data) result = _raw_poly1305.poly1305_update(self._state.get(), data_ptr, c_size_t(data_len)) if result: raise ValueError("Error %d while hashing Poly1305 data" % result) return self def copy(self): raise NotImplementedError() def digest(self) -> bytes: """Return the **binary** (non-printable) MAC tag of the message authenticated so far. :return: The MAC tag digest, computed over the data processed so far. Binary form. :rtype: byte string """ if self._mac_tag: return self._mac_tag bfr = create_string_buffer(16) result = _raw_poly1305.poly1305_digest(self._state.get(), bfr, c_size_t(len(bfr))) if result: raise ValueError("Error %d while creating Poly1305 digest" % result) self._mac_tag = get_raw_buffer(bfr) return self._mac_tag def hexdigest(self) -> str: """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 self.digest().hex() def verify(self, mac_tag: Buffer) -> None: """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: ValueError: if the MAC does not match. It means that the message has been tampered with or that the MAC key is incorrect. """ if not compare_digest(mac_tag, self.digest()): raise ValueError("MAC check failed") def hexverify(self, hex_mac_tag: str) -> None: """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( *, key: Buffer, cipher: ModuleType, nonce: Optional[Buffer] = None, data: Optional[Buffer] = None ) -> Poly1305_MAC: """Create a new Poly1305 MAC object. Args: key (bytes/bytearray/memoryview): The 32-byte key for the Poly1305 object. cipher (module from ``Crypto.Cipher``): The cipher algorithm to use for deriving the Poly1305 key pair *(r, s)*. It can only be ``Crypto.Cipher.AES`` or ``Crypto.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 """ if not hasattr(cipher, "_derive_Poly1305_key_pair"): raise ValueError("Parameter 'cipher' must be AES or ChaCha20") if key is None: raise TypeError("You must pass a parameter 'key'") r, s, nonce = cipher._derive_Poly1305_key_pair(key, nonce) new_mac = Poly1305_MAC(r, s, data) new_mac.nonce = bytes(nonce) # nonce may still be just a memoryview return new_mac