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# This file is adapted from Werkzeug (https://github.com/pallets/werkzeug)
# and is licensed under the BSD 3-Clause License:
# Copyright 2007 Pallets
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
# 3. Neither the name of the copyright holder nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
# TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
from __future__ import annotations
import hashlib
import hmac
import secrets
from deluge.error import InvalidHashError
SALT_CHARS = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
def gen_salt(length: int) -> str:
"""Generate a random string of SALT_CHARS with specified ``length``."""
if length <= 0:
raise ValueError('Salt length must be at least 1.')
return ''.join(secrets.choice(SALT_CHARS) for _ in range(length))
def _hash_internal(method: str, salt: str, password: str) -> tuple[str, str]:
method, *args = method.split('$')
salt_bytes = salt.encode()
password_bytes = password.encode()
if method == 'scrypt':
if not args:
n = 2**15
r = 8
p = 1
else:
try:
n, r, p = map(int, args)
except ValueError:
raise ValueError("'scrypt' takes 3 arguments.") from None
maxmem = 132 * n * r * p # ideally 128, but some extra seems needed
return (
hashlib.scrypt(
password_bytes, salt=salt_bytes, n=n, r=r, p=p, maxmem=maxmem
).hex(),
f'scrypt${n}${r}${p}',
)
else:
raise ValueError(f"Invalid hash method '{method}'.")
def generate_password_hash(
password: str, method: str = 'scrypt', salt_length: int = 16
) -> str:
"""Securely hash a password for storage. A password can be compared to a stored hash using check_password_hash.
Args:
password (str): The plaintext password to hash.
method (str): The key derivation function and parameters. Defaults to 'scrypt'.
salt_length (int): The length of the salt to generate. Defaults to 16.
Returns:
str: The hashed password in the format '$method$salt$hash'.
"""
salt = gen_salt(salt_length)
h, actual_method = _hash_internal(method, salt, password)
return f'${actual_method}${salt}${h}'
def check_password_hash(pwhash: str, password: str) -> bool:
"""Securely check that the given stored password hash, previously generated using
generate_password_hash, matches the given password.
Methods may be deprecated and removed if they are no longer considered secure. To
migrate old hashes, you may generate a new hash when checking an old hash, or you
may contact users with a link to reset their password.
Args:
pwhash (str): The hashed password in the format '$method$salt$hash
password (str): The plaintext password to check against the hash.
Raises:
ValueError: If the hash format is invalid or the method is not recognized.
Returns:
bool: True if the password matches the hash, False otherwise.
"""
method = None
try:
method, salt, stored_hash = pwhash.lstrip('$').rsplit('$', 2)
computed_hash = _hash_internal(method, salt, password)[0]
except ValueError as ve:
raise InvalidHashError(
'Invalid password hash format. Expected format: "$method$salt$hash".',
method=method if method else pwhash,
) from ve
return hmac.compare_digest(computed_hash, stored_hash)
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