298 lines
12 KiB
Python
298 lines
12 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# 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, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import base64
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import os
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import stat
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from cryptography import fernet
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from oslo_log import log
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from keystone.common import utils
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import keystone.conf
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LOG = log.getLogger(__name__)
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CONF = keystone.conf.CONF
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# NOTE(lbragstad): In the event there are no encryption keys on disk, let's use
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# a default one until a proper key repository is set up. This allows operators
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# to gracefully upgrade from Mitaka to Newton without a key repository,
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# especially in multi-node deployments. The NULL_KEY is specific to credential
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# encryption only and has absolutely no beneficial purpose outside of easing
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# upgrades.
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NULL_KEY = base64.urlsafe_b64encode(b'\x00' * 32)
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class FernetUtils(object):
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def __init__(self, key_repository=None, max_active_keys=None,
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config_group=None):
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self.key_repository = key_repository
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self.max_active_keys = max_active_keys
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self.config_group = config_group
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def validate_key_repository(self, requires_write=False):
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"""Validate permissions on the key repository directory."""
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# NOTE(lbragstad): We shouldn't need to check if the directory was
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# passed in as None because we don't set allow_no_values to True.
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# ensure current user has sufficient access to the key repository
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is_valid = (os.access(self.key_repository, os.R_OK) and
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os.access(self.key_repository, os.X_OK))
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if requires_write:
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is_valid = (is_valid and
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os.access(self.key_repository, os.W_OK))
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if not is_valid:
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LOG.error(
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'Either [%(config_group)s] key_repository does not exist '
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'or Keystone does not have sufficient permission to '
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'access it: %(key_repo)s',
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{'key_repo': self.key_repository,
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'config_group': self.config_group})
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else:
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# ensure the key repository isn't world-readable
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stat_info = os.stat(self.key_repository)
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if(stat_info.st_mode & stat.S_IROTH or
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stat_info.st_mode & stat.S_IXOTH):
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LOG.warning(
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'key_repository is world readable: %s',
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self.key_repository)
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return is_valid
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def create_key_directory(self, keystone_user_id=None,
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keystone_group_id=None):
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"""Attempt to create the key directory if it doesn't exist."""
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utils.create_directory(
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self.key_repository, keystone_user_id=keystone_user_id,
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keystone_group_id=keystone_group_id
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)
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def _create_new_key(self, keystone_user_id, keystone_group_id):
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"""Securely create a new encryption key.
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Create a new key that is readable by the Keystone group and Keystone
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user.
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To avoid disk write failure, this function will create a tmp key file
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first, and then rename it as the valid new key.
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"""
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self._create_tmp_new_key(keystone_user_id, keystone_group_id)
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self._become_valid_new_key()
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def _create_tmp_new_key(self, keystone_user_id, keystone_group_id):
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"""Securely create a new tmp encryption key.
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This created key is not effective until _become_valid_new_key().
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"""
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key = fernet.Fernet.generate_key() # key is bytes
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# This ensures the key created is not world-readable
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old_umask = os.umask(0o177)
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if keystone_user_id and keystone_group_id:
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old_egid = os.getegid()
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old_euid = os.geteuid()
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os.setegid(keystone_group_id)
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os.seteuid(keystone_user_id)
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elif keystone_user_id or keystone_group_id:
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LOG.warning(
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'Unable to change the ownership of the new key without a '
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'keystone user ID and keystone group ID both being provided: '
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'%s', self.key_repository)
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# Determine the file name of the new key
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key_file = os.path.join(self.key_repository, '0.tmp')
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create_success = False
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try:
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with open(key_file, 'w') as f:
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# convert key to str for the file.
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f.write(key.decode('utf-8'))
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f.flush()
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create_success = True
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except IOError:
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LOG.error('Failed to create new temporary key: %s', key_file)
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raise
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finally:
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# After writing the key, set the umask back to it's original value.
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# Do the same with group and user identifiers if a Keystone group
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# or user was supplied.
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os.umask(old_umask)
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if keystone_user_id and keystone_group_id:
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os.seteuid(old_euid)
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os.setegid(old_egid)
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# Deal with the tmp key file
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if not create_success and os.access(key_file, os.F_OK):
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os.remove(key_file)
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LOG.info('Created a new temporary key: %s', key_file)
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def _become_valid_new_key(self):
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"""Make the tmp new key a valid new key.
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The tmp new key must be created by _create_tmp_new_key().
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"""
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tmp_key_file = os.path.join(self.key_repository, '0.tmp')
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valid_key_file = os.path.join(self.key_repository, '0')
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os.rename(tmp_key_file, valid_key_file)
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LOG.info('Become a valid new key: %s', valid_key_file)
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def _get_key_files(self, key_repo):
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key_files = dict()
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keys = dict()
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for filename in os.listdir(key_repo):
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path = os.path.join(key_repo, str(filename))
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if os.path.isfile(path):
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with open(path, 'r') as key_file:
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try:
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key_id = int(filename)
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except ValueError: # nosec : name is not a number
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pass
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else:
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key = key_file.read()
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if len(key) == 0:
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LOG.warning('Ignoring empty key found in key '
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'repository: %s', path)
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continue
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key_files[key_id] = path
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keys[key_id] = key
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return key_files, keys
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def initialize_key_repository(self, keystone_user_id=None,
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keystone_group_id=None):
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"""Create a key repository and bootstrap it with a key.
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:param keystone_user_id: User ID of the Keystone user.
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:param keystone_group_id: Group ID of the Keystone user.
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"""
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# make sure we have work to do before proceeding
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if os.access(os.path.join(self.key_repository, '0'),
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os.F_OK):
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LOG.info('Key repository is already initialized; aborting.')
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return
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# bootstrap an existing key
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self._create_new_key(keystone_user_id, keystone_group_id)
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# ensure that we end up with a primary and secondary key
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self.rotate_keys(keystone_user_id, keystone_group_id)
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def rotate_keys(self, keystone_user_id=None, keystone_group_id=None):
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"""Create a new primary key and revoke excess active keys.
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:param keystone_user_id: User ID of the Keystone user.
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:param keystone_group_id: Group ID of the Keystone user.
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Key rotation utilizes the following behaviors:
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- The highest key number is used as the primary key (used for
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encryption).
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- All keys can be used for decryption.
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- New keys are always created as key "0," which serves as a placeholder
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before promoting it to be the primary key.
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This strategy allows you to safely perform rotation on one node in a
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cluster, before syncing the results of the rotation to all other nodes
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(during both key rotation and synchronization, all nodes must recognize
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all primary keys).
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"""
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# read the list of key files
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key_files, _ = self._get_key_files(self.key_repository)
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LOG.info('Starting key rotation with %(count)s key files: '
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'%(list)s', {
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'count': len(key_files),
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'list': list(key_files.values())})
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# add a tmp new key to the rotation, which will be the *next* primary
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self._create_tmp_new_key(keystone_user_id, keystone_group_id)
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# determine the number of the new primary key
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current_primary_key = max(key_files.keys())
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LOG.info('Current primary key is: %s', current_primary_key)
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new_primary_key = current_primary_key + 1
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LOG.info('Next primary key will be: %s', new_primary_key)
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# promote the next primary key to be the primary
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os.rename(
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os.path.join(self.key_repository, '0'),
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os.path.join(self.key_repository, str(new_primary_key))
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)
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key_files.pop(0)
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key_files[new_primary_key] = os.path.join(
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self.key_repository,
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str(new_primary_key))
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LOG.info('Promoted key 0 to be the primary: %s', new_primary_key)
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# rename the tmp key to the real staged key
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self._become_valid_new_key()
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max_active_keys = self.max_active_keys
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# purge excess keys
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# Note that key_files doesn't contain the new active key that was
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# created, only the old active keys.
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keys = sorted(key_files.keys(), reverse=True)
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while len(keys) > (max_active_keys - 1):
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index_to_purge = keys.pop()
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key_to_purge = key_files[index_to_purge]
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LOG.info('Excess key to purge: %s', key_to_purge)
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os.remove(key_to_purge)
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def load_keys(self, use_null_key=False):
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"""Load keys from disk into a list.
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The first key in the list is the primary key used for encryption. All
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other keys are active secondary keys that can be used for decrypting
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tokens.
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:param use_null_key: If true, a known key containing null bytes will be
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appended to the list of returned keys.
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"""
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if not self.validate_key_repository():
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if use_null_key:
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return [NULL_KEY]
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return []
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# build a dictionary of key_number:encryption_key pairs
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_, keys = self._get_key_files(self.key_repository)
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if len(keys) != self.max_active_keys:
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# Once the number of keys matches max_active_keys, this log entry
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# is too repetitive to be useful. Also note that it only makes
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# sense to log this message for tokens since credentials doesn't
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# have a `max_active_key` configuration option.
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if self.key_repository == CONF.fernet_tokens.key_repository:
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msg = ('Loaded %(count)d Fernet keys from %(dir)s, but '
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'`[fernet_tokens] max_active_keys = %(max)d`; perhaps '
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'there have not been enough key rotations to reach '
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'`max_active_keys` yet?')
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LOG.debug(msg, {
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'count': len(keys),
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'max': self.max_active_keys,
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'dir': self.key_repository})
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# return the encryption_keys, sorted by key number, descending
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key_list = [keys[x] for x in sorted(keys.keys(), reverse=True)]
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if use_null_key:
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key_list.append(NULL_KEY)
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return key_list
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