Source code for nacl.pwhash.scrypt

# Copyright 2013 Donald Stufft and individual contributors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from __future__ import absolute_import
from __future__ import division

import nacl.bindings
import nacl.encoding
from nacl import exceptions as exc
from nacl.exceptions import ensure

_strbytes_plus_one = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_STRBYTES

AVAILABLE = nacl.bindings.has_crypto_pwhash_scryptsalsa208sha256

STRPREFIX = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_STRPREFIX

SALTBYTES = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_SALTBYTES

PASSWD_MIN = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_PASSWD_MIN
PASSWD_MAX = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_PASSWD_MAX

PWHASH_SIZE = _strbytes_plus_one - 1

BYTES_MIN = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_BYTES_MIN
BYTES_MAX = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_BYTES_MAX

MEMLIMIT_MIN = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_MIN
MEMLIMIT_MAX = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_MAX
OPSLIMIT_MIN = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_MIN
OPSLIMIT_MAX = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_MAX

OPSLIMIT_INTERACTIVE = (
    nacl.bindings.crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_INTERACTIVE
)
MEMLIMIT_INTERACTIVE = (
    nacl.bindings.crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_INTERACTIVE
)
OPSLIMIT_SENSITIVE = (
    nacl.bindings.crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_SENSITIVE
)
MEMLIMIT_SENSITIVE = (
    nacl.bindings.crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_SENSITIVE
)

OPSLIMIT_MODERATE = 8 * OPSLIMIT_INTERACTIVE
MEMLIMIT_MODERATE = 8 * MEMLIMIT_INTERACTIVE


[docs]def kdf( size, password, salt, opslimit=OPSLIMIT_SENSITIVE, memlimit=MEMLIMIT_SENSITIVE, encoder=nacl.encoding.RawEncoder, ): """ Derive a ``size`` bytes long key from a caller-supplied ``password`` and ``salt`` pair using the scryptsalsa208sha256 memory-hard construct. the enclosing module provides the constants - :py:const:`.OPSLIMIT_INTERACTIVE` - :py:const:`.MEMLIMIT_INTERACTIVE` - :py:const:`.OPSLIMIT_SENSITIVE` - :py:const:`.MEMLIMIT_SENSITIVE` - :py:const:`.OPSLIMIT_MODERATE` - :py:const:`.MEMLIMIT_MODERATE` as a guidance for correct settings respectively for the interactive login and the long term key protecting sensitive data use cases. :param size: derived key size, must be between :py:const:`.BYTES_MIN` and :py:const:`.BYTES_MAX` :type size: int :param password: password used to seed the key derivation procedure; it length must be between :py:const:`.PASSWD_MIN` and :py:const:`.PASSWD_MAX` :type password: bytes :param salt: **RANDOM** salt used in the key derivation procedure; its length must be exactly :py:const:`.SALTBYTES` :type salt: bytes :param opslimit: the time component (operation count) of the key derivation procedure's computational cost; it must be between :py:const:`.OPSLIMIT_MIN` and :py:const:`.OPSLIMIT_MAX` :type opslimit: int :param memlimit: the memory occupation component of the key derivation procedure's computational cost; it must be between :py:const:`.MEMLIMIT_MIN` and :py:const:`.MEMLIMIT_MAX` :type memlimit: int :rtype: bytes :raises nacl.exceptions.UnavailableError: If called when using a minimal build of libsodium. .. versionadded:: 1.2 """ ensure( AVAILABLE, "Not available in minimal build", raising=exc.UnavailableError, ) ensure( len(salt) == SALTBYTES, "The salt must be exactly %s, not %s bytes long" % (SALTBYTES, len(salt)), raising=exc.ValueError, ) n_log2, r, p = nacl.bindings.nacl_bindings_pick_scrypt_params( opslimit, memlimit ) maxmem = memlimit + (2 ** 16) return encoder.encode( nacl.bindings.crypto_pwhash_scryptsalsa208sha256_ll( password, salt, 2 ** n_log2, r, p, maxmem=maxmem, dklen=size ) )
[docs]def str( password, opslimit=OPSLIMIT_INTERACTIVE, memlimit=MEMLIMIT_INTERACTIVE ): """ Hashes a password with a random salt, using the memory-hard scryptsalsa208sha256 construct and returning an ascii string that has all the needed info to check against a future password The default settings for opslimit and memlimit are those deemed correct for the interactive user login case. :param bytes password: :param int opslimit: :param int memlimit: :rtype: bytes :raises nacl.exceptions.UnavailableError: If called when using a minimal build of libsodium. .. versionadded:: 1.2 """ ensure( AVAILABLE, "Not available in minimal build", raising=exc.UnavailableError, ) return nacl.bindings.crypto_pwhash_scryptsalsa208sha256_str( password, opslimit, memlimit )
[docs]def verify(password_hash, password): """ Takes the output of scryptsalsa208sha256 and compares it against a user provided password to see if they are the same :param password_hash: bytes :param password: bytes :rtype: boolean :raises nacl.exceptions.UnavailableError: If called when using a minimal build of libsodium. .. versionadded:: 1.2 """ ensure( AVAILABLE, "Not available in minimal build", raising=exc.UnavailableError, ) ensure( len(password_hash) == PWHASH_SIZE, "The password hash must be exactly %s bytes long" % nacl.bindings.crypto_pwhash_scryptsalsa208sha256_STRBYTES, raising=exc.ValueError, ) return nacl.bindings.crypto_pwhash_scryptsalsa208sha256_str_verify( password_hash, password )