167 lines
5.9 KiB
Python
167 lines
5.9 KiB
Python
# Copyright 2013 Donald Stufft and individual contributors
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from __future__ import absolute_import
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from __future__ import division
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import nacl.bindings
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import nacl.encoding
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from nacl import exceptions as exc
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from nacl.exceptions import ensure
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_strbytes_plus_one = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_STRBYTES
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STRPREFIX = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_STRPREFIX
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SALTBYTES = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_SALTBYTES
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PASSWD_MIN = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_PASSWD_MIN
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PASSWD_MAX = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_PASSWD_MAX
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PWHASH_SIZE = _strbytes_plus_one - 1
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BYTES_MIN = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_BYTES_MIN
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BYTES_MAX = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_BYTES_MAX
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MEMLIMIT_MIN = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_MIN
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MEMLIMIT_MAX = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_MAX
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OPSLIMIT_MIN = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_MIN
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OPSLIMIT_MAX = nacl.bindings.crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_MAX
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OPSLIMIT_INTERACTIVE = \
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nacl.bindings.crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_INTERACTIVE
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MEMLIMIT_INTERACTIVE = \
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nacl.bindings.crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_INTERACTIVE
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OPSLIMIT_SENSITIVE = \
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nacl.bindings.crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_SENSITIVE
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MEMLIMIT_SENSITIVE = \
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nacl.bindings.crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_SENSITIVE
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OPSLIMIT_MODERATE = 8 * OPSLIMIT_INTERACTIVE
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MEMLIMIT_MODERATE = 8 * MEMLIMIT_INTERACTIVE
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def kdf(size, password, salt,
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opslimit=OPSLIMIT_SENSITIVE,
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memlimit=MEMLIMIT_SENSITIVE,
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encoder=nacl.encoding.RawEncoder):
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"""
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Derive a ``size`` bytes long key from a caller-supplied
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``password`` and ``salt`` pair using the scryptsalsa208sha256
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memory-hard construct.
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the enclosing module provides the constants
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- :py:const:`.OPSLIMIT_INTERACTIVE`
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- :py:const:`.MEMLIMIT_INTERACTIVE`
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- :py:const:`.OPSLIMIT_SENSITIVE`
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- :py:const:`.MEMLIMIT_SENSITIVE`
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- :py:const:`.OPSLIMIT_MODERATE`
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- :py:const:`.MEMLIMIT_MODERATE`
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as a guidance for correct settings respectively for the
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interactive login and the long term key protecting sensitive data
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use cases.
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:param size: derived key size, must be between
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:py:const:`.BYTES_MIN` and
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:py:const:`.BYTES_MAX`
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:type size: int
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:param password: password used to seed the key derivation procedure;
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it length must be between
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:py:const:`.PASSWD_MIN` and
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:py:const:`.PASSWD_MAX`
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:type password: bytes
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:param salt: **RANDOM** salt used in the key derivation procedure;
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its length must be exactly :py:const:`.SALTBYTES`
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:type salt: bytes
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:param opslimit: the time component (operation count)
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of the key derivation procedure's computational cost;
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it must be between
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:py:const:`.OPSLIMIT_MIN` and
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:py:const:`.OPSLIMIT_MAX`
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:type opslimit: int
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:param memlimit: the memory occupation component
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of the key derivation procedure's computational cost;
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it must be between
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:py:const:`.MEMLIMIT_MIN` and
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:py:const:`.MEMLIMIT_MAX`
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:type memlimit: int
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:rtype: bytes
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.. versionadded:: 1.2
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"""
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ensure(
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len(salt) == SALTBYTES,
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"The salt must be exactly %s, not %s bytes long" % (
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SALTBYTES,
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len(salt)
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),
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raising=exc.ValueError
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)
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n_log2, r, p = nacl.bindings.nacl_bindings_pick_scrypt_params(opslimit,
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memlimit)
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maxmem = memlimit + (2 ** 16)
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return encoder.encode(
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nacl.bindings.crypto_pwhash_scryptsalsa208sha256_ll(
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password, salt, 2 ** n_log2, r, p, maxmem=maxmem, dklen=size)
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)
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def str(password,
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opslimit=OPSLIMIT_INTERACTIVE,
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memlimit=MEMLIMIT_INTERACTIVE):
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"""
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Hashes a password with a random salt, using the memory-hard
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scryptsalsa208sha256 construct and returning an ascii string
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that has all the needed info to check against a future password
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The default settings for opslimit and memlimit are those deemed
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correct for the interactive user login case.
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:param bytes password:
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:param int opslimit:
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:param int memlimit:
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:rtype: bytes
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.. versionadded:: 1.2
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"""
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return nacl.bindings.crypto_pwhash_scryptsalsa208sha256_str(password,
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opslimit,
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memlimit)
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def verify(password_hash, password):
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"""
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Takes the output of scryptsalsa208sha256 and compares it against
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a user provided password to see if they are the same
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:param password_hash: bytes
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:param password: bytes
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:rtype: boolean
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.. versionadded:: 1.2
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"""
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ensure(len(password_hash) == PWHASH_SIZE,
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"The password hash must be exactly %s bytes long" %
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nacl.bindings.crypto_pwhash_scryptsalsa208sha256_STRBYTES,
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raising=exc.ValueError)
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return nacl.bindings.crypto_pwhash_scryptsalsa208sha256_str_verify(
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password_hash, password
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)
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