pycryptodome/lib/Crypto/Hash/BLAKE2s.py

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"""BLAKE2s cryptographic hash algorithm.

`BLAKE2s`_ is an optimized variant of BLAKE, one of the SHA-3 candidates that
made it to the final round of the NIST hash competition.

The algorithm uses 32 bit words, and it therefore works best
on 32-bit platforms. The digest size ranges from 8 to 256 bits.

    >>> from Crypto.Hash import BLAKE2s
    >>>
    >>> h_obj = BLAKE2s.new(digest_bits=256)
    >>> h_obj.update(b'Some data')
    >>> print h_obj.hexdigest()

Optionally, BLAKE2s can work as a cryptographic MAC when initialized
with a secret key.

    >>> from Crypto.Hash import BLAKE2s
    >>>
    >>> mac = BLAKE2s.new(digest_bits=128, key=b'secret')
    >>> mac.update(b'Some data')
    >>> print mac.hexdigest()

:undocumented: __package__

.. _BLAKE2s: https://blake2.net/
"""

from binascii import unhexlify

from Crypto.Util.py3compat import b, bord, tobytes

from Crypto.Random import get_random_bytes
from Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
                                  VoidPointer, SmartPointer,
                                  create_string_buffer,
                                  get_raw_buffer, c_size_t,
                                  expect_byte_string)

_raw_blake2s_lib = load_pycryptodome_raw_lib("Crypto.Hash._BLAKE2s",
                        """
                        int blake2s_init(void **state,
                                         const uint8_t *key,
                                         size_t key_size,
                                         size_t digest_size);
                        int blake2s_destroy(void *state);
                        int blake2s_update(void *state,
                                           const uint8_t *buf,
                                           size_t len);
                        int blake2s_digest(const void *state,
                                           uint8_t digest[32]);
                        int blake2s_copy(const void *src, void *dst);
                        """)


class BLAKE2s_Hash(object):
    """Class that implements a BLAKE2s hash
    """

    #: The internal block size of the hash algorithm in bytes.
    block_size = 32

    def __init__(self, data, key, digest_bytes):
        """
        Initialize a BLAKE2s hash object.
        """

        #: The size of the resulting hash in bytes.
        self.digest_size = digest_bytes

        # See https://tools.ietf.org/html/draft-saarinen-blake2-02
        if digest_bytes in (16, 20, 28, 32) and not key:
            self.oid = "1.3.6.1.4.1.1722.12.2.2." + str(digest_bytes)

        expect_byte_string(key)

        state = VoidPointer()
        result = _raw_blake2s_lib.blake2s_init(state.address_of(),
                                               key,
                                               c_size_t(len(key)),
                                               c_size_t(digest_bytes)
                                               )
        if result:
            raise ValueError("Error %d while instantiating BLAKE2s" % result)
        self._state = SmartPointer(state.get(),
                                   _raw_blake2s_lib.blake2s_destroy)
        if data:
            self.update(data)

    def update(self, data):
        """Continue hashing of a message by consuming the next chunk of data.

        Repeated calls are equivalent to a single call with the concatenation
        of all the arguments. In other words:

           >>> m.update(a); m.update(b)

        is equivalent to:

           >>> m.update(a+b)

        :Parameters:
          data : byte string
            The next chunk of the message being hashed.
        """

        expect_byte_string(data)
        result = _raw_blake2s_lib.blake2s_update(self._state.get(),
                                                 data,
                                                 c_size_t(len(data)))
        if result:
            raise ValueError("Error %d while hashing BLAKE2s data" % result)
        return self

    def digest(self):
        """Return the **binary** (non-printable) digest of the message that
        has been hashed so far.

        This method does not change the state of the hash object.
        You can continue updating the object after calling this function.

        :Return: A byte string of `digest_size` bytes. It may contain non-ASCII
         characters, including null bytes.
        """

        bfr = create_string_buffer(32)
        result = _raw_blake2s_lib.blake2s_digest(self._state.get(),
                                                 bfr)
        if result:
            raise ValueError("Error %d while creating BLAKE2s digest" % result)

        return get_raw_buffer(bfr)[:self.digest_size]

    def hexdigest(self):
        """Return the **printable** digest of the message that has been hashed
        so far.

        This method does not change the state of the hash object.

        :Return: A string of 2* `digest_size` characters. It contains only
         hexadecimal ASCII digits.
        """

        return "".join(["%02x" % bord(x) for x in tuple(self.digest())])

    def copy(self):
        """Return a copy ("clone") of the hash object.

        The copy will have the same internal state as the original hash
        object.
        This can be used to efficiently compute the digests of strings that
        share a common initial substring.

        :Return: A hash object of the same type
        """

        clone = BLAKE2s_Hash(None, b(""), self.digest_size)
        result = _raw_blake2s_lib.blake2s_copy(self._state.get(),
                                               clone._state.get())
        if result:
            raise ValueError("Error %d while copying BLAKE2s" % result)
        return clone

    def verify(self, mac_tag):
        """Verify that a given **binary** MAC (computed by another party)
        is valid.

        :Parameters:
          mac_tag : byte string
            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.
        """

        secret = get_random_bytes(16)

        mac1 = new(digest_bits=160, key=secret, data=mac_tag)
        mac2 = 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.

        :Parameters:
          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(self, **kwargs):
        """Return a new instance of a BLAKE2s hash object."""

        if "digest_bytes" not in kwargs and "digest_bits" not in kwargs:
            kwargs["digest_bytes"] = self.digest_size

        return new(**kwargs)


def new(**kwargs):
    """Return a new instance of a BLAKE2s hash object.

    :Keywords:
      data : byte string
        The very first chunk of the message to hash.
        It is equivalent to an early call to `BLAKE2s_Hash.update()`.
      digest_bytes : integer
        The size of the digest, in bytes (1 to 32).
      digest_bits : integer
        The size of the digest, in bits (8 to 256, in steps of 8).
      key : byte string
        The key to use to compute the MAC (1 to 32 bytes).
        If not specified, no key will be used.
    :Return: A `BLAKE2s_Hash` object
    """

    data = kwargs.pop("data", None)

    digest_bytes = kwargs.pop("digest_bytes", None)
    digest_bits = kwargs.pop("digest_bits", None)
    if None not in (digest_bytes, digest_bits):
        raise TypeError("Only one digest parameter must be provided")
    if (None, None) == (digest_bytes, digest_bits):
        raise TypeError("Digest size (bits, bytes) not provided")
    if digest_bytes is not None:
        if not (1 <= digest_bytes <= 32):
            raise ValueError("'digest_bytes' not in range 1..32")
    else:
        if not (8 <= digest_bits <= 256) or (digest_bits % 8):
            raise ValueError("'digest_bytes' not in range 8..256, "
                             "with steps of 8")
        digest_bytes = digest_bits // 8

    key = kwargs.pop("key", b(""))
    if len(key) > 32:
        raise ValueError("BLAKE2s key cannot exceed 32 bytes")

    if kwargs:
        raise TypeError("Unknown parameters: " + str(kwargs))

    return BLAKE2s_Hash(data, key, digest_bytes)