Source code for keystone.common.fernet_utils

# 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
# 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 base64
import os
import stat

from cryptography import fernet
from oslo_log import log

from keystone.common import utils
import keystone.conf

LOG = log.getLogger(__name__)

CONF = keystone.conf.CONF

# NOTE(lbragstad): In the event there are no encryption keys on disk, let's use
# a default one until a proper key repository is set up. This allows operators
# to gracefully upgrade from Mitaka to Newton without a key repository,
# especially in multi-node deployments. The NULL_KEY is specific to credential
# encryption only and has absolutely no beneficial purpose outside of easing
# upgrades.
NULL_KEY = base64.urlsafe_b64encode(b'\x00' * 32)

[docs]class FernetUtils(object): def __init__(self, key_repository=None, max_active_keys=None, config_group=None): self.key_repository = key_repository self.max_active_keys = max_active_keys self.config_group = config_group
[docs] def validate_key_repository(self, requires_write=False): """Validate permissions on the key repository directory.""" # NOTE(lbragstad): We shouldn't need to check if the directory was # passed in as None because we don't set allow_no_values to True. # ensure current user has sufficient access to the key repository is_valid = (os.access(self.key_repository, os.R_OK) and os.access(self.key_repository, os.X_OK)) if requires_write: is_valid = (is_valid and os.access(self.key_repository, os.W_OK)) if not is_valid: LOG.error( 'Either [%(config_group)s] key_repository does not exist ' 'or Keystone does not have sufficient permission to ' 'access it: %(key_repo)s', {'key_repo': self.key_repository, 'config_group': self.config_group}) else: # ensure the key repository isn't world-readable stat_info = os.stat(self.key_repository) if(stat_info.st_mode & stat.S_IROTH or stat_info.st_mode & stat.S_IXOTH): LOG.warning( 'key_repository is world readable: %s', self.key_repository) return is_valid
[docs] def create_key_directory(self, keystone_user_id=None, keystone_group_id=None): """Attempt to create the key directory if it doesn't exist.""" utils.create_directory( self.key_repository, keystone_user_id=keystone_user_id, keystone_group_id=keystone_group_id )
def _create_new_key(self, keystone_user_id, keystone_group_id): """Securely create a new encryption key. Create a new key that is readable by the Keystone group and Keystone user. To avoid disk write failure, this function will create a tmp key file first, and then rename it as the valid new key. """ self._create_tmp_new_key(keystone_user_id, keystone_group_id) self._become_valid_new_key() def _create_tmp_new_key(self, keystone_user_id, keystone_group_id): """Securely create a new tmp encryption key. This created key is not effective until _become_valid_new_key(). """ key = fernet.Fernet.generate_key() # key is bytes # This ensures the key created is not world-readable old_umask = os.umask(0o177) if keystone_user_id and keystone_group_id: old_egid = os.getegid() old_euid = os.geteuid() os.setegid(keystone_group_id) os.seteuid(keystone_user_id) elif keystone_user_id or keystone_group_id: LOG.warning( 'Unable to change the ownership of the new key without a ' 'keystone user ID and keystone group ID both being provided: ' '%s', self.key_repository) # Determine the file name of the new key key_file = os.path.join(self.key_repository, '0.tmp') create_success = False try: with open(key_file, 'w') as f: # convert key to str for the file. f.write(key.decode('utf-8')) f.flush() create_success = True except IOError: LOG.error('Failed to create new temporary key: %s', key_file) raise finally: # After writing the key, set the umask back to it's original value. # Do the same with group and user identifiers if a Keystone group # or user was supplied. os.umask(old_umask) if keystone_user_id and keystone_group_id: os.seteuid(old_euid) os.setegid(old_egid) # Deal with the tmp key file if not create_success and os.access(key_file, os.F_OK): os.remove(key_file)'Created a new temporary key: %s', key_file) def _become_valid_new_key(self): """Make the tmp new key a valid new key. The tmp new key must be created by _create_tmp_new_key(). """ tmp_key_file = os.path.join(self.key_repository, '0.tmp') valid_key_file = os.path.join(self.key_repository, '0') os.rename(tmp_key_file, valid_key_file)'Become a valid new key: %s', valid_key_file) def _get_key_files(self, key_repo): key_files = dict() keys = dict() for filename in os.listdir(key_repo): path = os.path.join(key_repo, str(filename)) if os.path.isfile(path): with open(path, 'r') as key_file: try: key_id = int(filename) except ValueError: # nosec : name is not a number pass else: key = if len(key) == 0: LOG.warning('Ignoring empty key found in key ' 'repository: %s', path) continue key_files[key_id] = path keys[key_id] = key return key_files, keys
[docs] def initialize_key_repository(self, keystone_user_id=None, keystone_group_id=None): """Create a key repository and bootstrap it with a key. :param keystone_user_id: User ID of the Keystone user. :param keystone_group_id: Group ID of the Keystone user. """ # make sure we have work to do before proceeding if os.access(os.path.join(self.key_repository, '0'), os.F_OK):'Key repository is already initialized; aborting.') return # bootstrap an existing key self._create_new_key(keystone_user_id, keystone_group_id) # ensure that we end up with a primary and secondary key self.rotate_keys(keystone_user_id, keystone_group_id)
[docs] def rotate_keys(self, keystone_user_id=None, keystone_group_id=None): """Create a new primary key and revoke excess active keys. :param keystone_user_id: User ID of the Keystone user. :param keystone_group_id: Group ID of the Keystone user. Key rotation utilizes the following behaviors: - The highest key number is used as the primary key (used for encryption). - All keys can be used for decryption. - New keys are always created as key "0," which serves as a placeholder before promoting it to be the primary key. This strategy allows you to safely perform rotation on one node in a cluster, before syncing the results of the rotation to all other nodes (during both key rotation and synchronization, all nodes must recognize all primary keys). """ # read the list of key files key_files, _ = self._get_key_files(self.key_repository)'Starting key rotation with %(count)s key files: ' '%(list)s', { 'count': len(key_files), 'list': list(key_files.values())}) # add a tmp new key to the rotation, which will be the *next* primary self._create_tmp_new_key(keystone_user_id, keystone_group_id) # determine the number of the new primary key current_primary_key = max(key_files.keys())'Current primary key is: %s', current_primary_key) new_primary_key = current_primary_key + 1'Next primary key will be: %s', new_primary_key) # promote the next primary key to be the primary os.rename( os.path.join(self.key_repository, '0'), os.path.join(self.key_repository, str(new_primary_key)) ) key_files.pop(0) key_files[new_primary_key] = os.path.join( self.key_repository, str(new_primary_key))'Promoted key 0 to be the primary: %s', new_primary_key) # rename the tmp key to the real staged key self._become_valid_new_key() max_active_keys = self.max_active_keys # purge excess keys # Note that key_files doesn't contain the new active key that was # created, only the old active keys. keys = sorted(key_files.keys(), reverse=True) while len(keys) > (max_active_keys - 1): index_to_purge = keys.pop() key_to_purge = key_files[index_to_purge]'Excess key to purge: %s', key_to_purge) os.remove(key_to_purge)
[docs] def load_keys(self, use_null_key=False): """Load keys from disk into a list. The first key in the list is the primary key used for encryption. All other keys are active secondary keys that can be used for decrypting tokens. :param use_null_key: If true, a known key containing null bytes will be appended to the list of returned keys. """ if not self.validate_key_repository(): if use_null_key: return [NULL_KEY] return [] # build a dictionary of key_number:encryption_key pairs _, keys = self._get_key_files(self.key_repository) if len(keys) != self.max_active_keys: # Once the number of keys matches max_active_keys, this log entry # is too repetitive to be useful. Also note that it only makes # sense to log this message for tokens since credentials doesn't # have a `max_active_key` configuration option. if self.key_repository == CONF.fernet_tokens.key_repository: msg = ('Loaded %(count)d Fernet keys from %(dir)s, but ' '`[fernet_tokens] max_active_keys = %(max)d`; perhaps ' 'there have not been enough key rotations to reach ' '`max_active_keys` yet?') LOG.debug(msg, { 'count': len(keys), 'max': self.max_active_keys, 'dir': self.key_repository}) # return the encryption_keys, sorted by key number, descending key_list = [keys[x] for x in sorted(keys.keys(), reverse=True)] if use_null_key: key_list.append(NULL_KEY) return key_list