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# Copyright 2012 Nebula, Inc.
#
# 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 logging
import os
import random
import string
from oslo_concurrency import lockutils
class FilePermissionError(Exception):
"""The key file permissions are insecure."""
pass
def generate_key(key_length=64):
"""Secret key generator.
The quality of randomness depends on operating system support,
see http://docs.python.org/library/random.html#random.SystemRandom.
"""
if hasattr(random, 'SystemRandom'):
logging.info('Generating a secure random key using SystemRandom.')
choice = random.SystemRandom().choice
else:
msg = "WARNING: SystemRandom not present. Generating a random "\
"key using random.choice (NOT CRYPTOGRAPHICALLY SECURE)."
logging.warning(msg)
choice = random.choice
return ''.join(map(lambda x: choice(string.digits + string.ascii_letters),
range(key_length)))
def read_from_file(key_file='.secret_key'):
if (os.stat(key_file).st_mode & 0o777) != 0o600:
raise FilePermissionError(
"Insecure permissions on key file %s, should be 0600." %
os.path.abspath(key_file))
with open(key_file, 'r') as f:
key = f.readline()
return key
def generate_or_read_from_file(key_file='.secret_key', key_length=64):
"""Multiprocess-safe secret key file generator.
Useful to replace the default (and thus unsafe) SECRET_KEY in settings.py
upon first start. Save to use, i.e. when multiple Python interpreters
serve the dashboard Django application (e.g. in a mod_wsgi + daemonized
environment). Also checks if file permissions are set correctly and
throws an exception if not.
"""
abspath = os.path.abspath(key_file)
# check, if key_file already exists
# if yes, then just read and return key
if os.path.exists(key_file):
key = read_from_file(key_file)
return key
# otherwise, first lock to make sure only one process
lock = lockutils.external_lock(key_file + ".lock",
lock_path=os.path.dirname(abspath))
with lock:
if not os.path.exists(key_file):
key = generate_key(key_length)
old_umask = os.umask(0o177) # Use '0600' file permissions
with open(key_file, 'w') as f:
f.write(key)
os.umask(old_umask)
else:
key = read_from_file(key_file)
return key