# Copyright 2022 Karlsruhe Institute of Technology
#
# 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.
import hashlib
import os
import string
from secrets import SystemRandom
from time import time
import jwt
from flask import current_app
[docs]def random_alnum(num_chars=16):
"""Generate a secure random alphanumeric string.
:param num_chars: (optional) The number of chars to generate.
:return: The generated string.
"""
alphanum = string.ascii_letters + string.digits
return "".join(SystemRandom().choice(alphanum) for _ in range(num_chars))
[docs]def random_bytes(num_bytes=24, hexadecimal=True):
"""Generate a secure random byte sequence.
:param length: (optional) The number of bytes to generate.
:param hexadecimal: (optional) Whether to return the bytes in a hexadecimal string
representation.
:return: The generated byte sequence or hexadecimal string.
"""
byte_sequence = os.urandom(num_bytes)
if hexadecimal:
return byte_sequence.hex()
return byte_sequence
[docs]def hash_value(value, alg="sha256", hexadecimal=True):
"""Create a secure hash of a value.
:param value: The value to hash, either a bytes-like object or a string.
:param alg: (optional) The hash algorithm to use, according to the algorithms
available in Python's "hashlib" module.
:param hexadecimal: (optional) Whether to return the hash in a hexadecimal string
representation.
:return: The calculated hash as a byte sequence or hexadecimal string or ``None`` if
the given algorithm is not available.
"""
try:
memoryview(value)
except TypeError:
value = value.encode()
if alg not in hashlib.algorithms_available:
return None
hashed_value = getattr(hashlib, alg)(value)
if hexadecimal:
return hashed_value.hexdigest()
return hashed_value.digest()
[docs]def encode_jwt(payload, expires_in=None):
"""Encode a given payload inside a JSON web token.
:param payload: The payload to encode as dictionary, which needs to be JSON
serializable.
:param expires_in: (optional) The time in seconds that the token should expire in.
:return: The encoded token as string.
"""
if expires_in is not None:
payload["exp"] = int(time()) + expires_in
return jwt.encode(payload, current_app.secret_key, algorithm="HS256")
[docs]def decode_jwt(token):
"""Decode a given JSON web token.
:param token: The token to decode as string.
:return: The decoded payload dictionary or ``None`` if the token is invalid or
expired.
"""
try:
return jwt.decode(token, current_app.secret_key, algorithms=["HS256"])
except jwt.InvalidTokenError:
return None