304 lines
10 KiB
Python
304 lines
10 KiB
Python
# Copyright 2018 Catalyst Cloud Ltd
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#
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# 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 datetime
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import struct
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import uuid
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from cryptography import fernet
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import msgpack
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from oslo_log import log
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from oslo_utils import timeutils
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from keystone.auth import plugins as auth_plugins
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from keystone.common import fernet_utils as utils
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from keystone.common import utils as ks_utils
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import keystone.conf
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from keystone import exception
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from keystone.i18n import _
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CONF = keystone.conf.CONF
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LOG = log.getLogger(__name__)
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# Fernet byte indexes as computed by pypi/keyless_fernet and defined in
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# https://github.com/fernet/spec
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TIMESTAMP_START = 1
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TIMESTAMP_END = 9
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class ReceiptFormatter(object):
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"""Packs and unpacks payloads into receipts for transport."""
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@property
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def crypto(self):
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"""Return a cryptography instance.
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You can extend this class with a custom crypto @property to provide
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your own receipt encoding / decoding. For example, using a different
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cryptography library (e.g. ``python-keyczar``) or to meet arbitrary
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security requirements.
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This @property just needs to return an object that implements
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``encrypt(plaintext)`` and ``decrypt(ciphertext)``.
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"""
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fernet_utils = utils.FernetUtils(
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CONF.fernet_receipts.key_repository,
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CONF.fernet_receipts.max_active_keys,
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'fernet_receipts'
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)
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keys = fernet_utils.load_keys()
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if not keys:
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raise exception.KeysNotFound()
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fernet_instances = [fernet.Fernet(key) for key in keys]
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return fernet.MultiFernet(fernet_instances)
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def pack(self, payload):
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"""Pack a payload for transport as a receipt.
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:type payload: six.binary_type
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:rtype: six.text_type
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"""
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# base64 padding (if any) is not URL-safe
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return self.crypto.encrypt(payload).rstrip(b'=').decode('utf-8')
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def unpack(self, receipt):
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"""Unpack a receipt, and validate the payload.
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:type receipt: six.text_type
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:rtype: six.binary_type
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"""
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receipt = ReceiptFormatter.restore_padding(receipt)
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try:
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return self.crypto.decrypt(receipt.encode('utf-8'))
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except fernet.InvalidToken:
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raise exception.ValidationError(
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_('This is not a recognized Fernet receipt %s') % receipt)
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@classmethod
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def restore_padding(cls, receipt):
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"""Restore padding based on receipt size.
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:param receipt: receipt to restore padding on
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:type receipt: six.text_type
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:returns: receipt with correct padding
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"""
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# Re-inflate the padding
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mod_returned = len(receipt) % 4
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if mod_returned:
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missing_padding = 4 - mod_returned
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receipt += '=' * missing_padding
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return receipt
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@classmethod
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def creation_time(cls, fernet_receipt):
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"""Return the creation time of a valid Fernet receipt.
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:type fernet_receipt: six.text_type
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"""
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fernet_receipt = ReceiptFormatter.restore_padding(fernet_receipt)
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# fernet_receipt is six.text_type
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# Fernet receipts are base64 encoded, so we need to unpack them first
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# urlsafe_b64decode() requires six.binary_type
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receipt_bytes = base64.urlsafe_b64decode(
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fernet_receipt.encode('utf-8'))
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# slice into the byte array to get just the timestamp
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timestamp_bytes = receipt_bytes[TIMESTAMP_START:TIMESTAMP_END]
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# convert those bytes to an integer
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# (it's a 64-bit "unsigned long long int" in C)
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timestamp_int = struct.unpack(">Q", timestamp_bytes)[0]
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# and with an integer, it's trivial to produce a datetime object
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issued_at = datetime.datetime.utcfromtimestamp(timestamp_int)
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return issued_at
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def create_receipt(self, user_id, methods, expires_at):
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"""Given a set of payload attributes, generate a Fernet receipt."""
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payload = ReceiptPayload.assemble(user_id, methods, expires_at)
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serialized_payload = msgpack.packb(payload)
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receipt = self.pack(serialized_payload)
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# NOTE(lbragstad): We should warn against Fernet receipts that are over
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# 255 characters in length. This is mostly due to persisting the
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# receipts in a backend store of some kind that might have a limit of
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# 255 characters. Even though Keystone isn't storing a Fernet receipt
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# anywhere, we can't say it isn't being stored somewhere else with
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# those kind of backend constraints.
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if len(receipt) > 255:
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LOG.info('Fernet receipt created with length of %d '
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'characters, which exceeds 255 characters',
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len(receipt))
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return receipt
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def validate_receipt(self, receipt):
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"""Validate a Fernet receipt and returns the payload attributes.
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:type receipt: six.text_type
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"""
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serialized_payload = self.unpack(receipt)
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payload = msgpack.unpackb(serialized_payload)
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(user_id, methods, expires_at) = ReceiptPayload.disassemble(payload)
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# rather than appearing in the payload, the creation time is encoded
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# into the receipt format itself
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issued_at = ReceiptFormatter.creation_time(receipt)
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issued_at = ks_utils.isotime(at=issued_at, subsecond=True)
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expires_at = timeutils.parse_isotime(expires_at)
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expires_at = ks_utils.isotime(at=expires_at, subsecond=True)
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return (user_id, methods, issued_at, expires_at)
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class ReceiptPayload(object):
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@classmethod
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def assemble(cls, user_id, methods, expires_at):
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"""Assemble the payload of a receipt.
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:param user_id: identifier of the user in the receipt request
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:param methods: list of authentication methods used
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:param expires_at: datetime of the receipt's expiration
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:returns: the payload of a receipt
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"""
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b_user_id = cls.attempt_convert_uuid_hex_to_bytes(user_id)
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methods = auth_plugins.convert_method_list_to_integer(methods)
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expires_at_int = cls._convert_time_string_to_float(expires_at)
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return (b_user_id, methods, expires_at_int)
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@classmethod
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def disassemble(cls, payload):
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"""Disassemble a payload into the component data.
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The tuple consists of::
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(user_id, methods, expires_at_str)
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* ``methods`` are the auth methods.
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:param payload: this variant of payload
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:returns: a tuple of the payloads component data
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"""
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(is_stored_as_bytes, user_id) = payload[0]
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if is_stored_as_bytes:
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user_id = cls.convert_uuid_bytes_to_hex(user_id)
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methods = auth_plugins.convert_integer_to_method_list(payload[1])
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expires_at_str = cls._convert_float_to_time_string(payload[2])
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return (user_id, methods, expires_at_str)
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@classmethod
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def convert_uuid_hex_to_bytes(cls, uuid_string):
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"""Compress UUID formatted strings to bytes.
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:param uuid_string: uuid string to compress to bytes
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:returns: a byte representation of the uuid
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"""
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uuid_obj = uuid.UUID(uuid_string)
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return uuid_obj.bytes
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@classmethod
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def convert_uuid_bytes_to_hex(cls, uuid_byte_string):
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"""Generate uuid.hex format based on byte string.
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:param uuid_byte_string: uuid string to generate from
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:returns: uuid hex formatted string
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"""
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uuid_obj = uuid.UUID(bytes=uuid_byte_string)
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return uuid_obj.hex
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@classmethod
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def _convert_time_string_to_float(cls, time_string):
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"""Convert a time formatted string to a float.
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:param time_string: time formatted string
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:returns: a timestamp as a float
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"""
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time_object = timeutils.parse_isotime(time_string)
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return (timeutils.normalize_time(time_object) -
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datetime.datetime.utcfromtimestamp(0)).total_seconds()
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@classmethod
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def _convert_float_to_time_string(cls, time_float):
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"""Convert a floating point timestamp to a string.
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:param time_float: integer representing timestamp
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:returns: a time formatted strings
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"""
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time_object = datetime.datetime.utcfromtimestamp(time_float)
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return ks_utils.isotime(time_object, subsecond=True)
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@classmethod
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def attempt_convert_uuid_hex_to_bytes(cls, value):
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"""Attempt to convert value to bytes or return value.
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:param value: value to attempt to convert to bytes
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:returns: tuple containing boolean indicating whether user_id was
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stored as bytes and uuid value as bytes or the original value
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"""
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try:
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return (True, cls.convert_uuid_hex_to_bytes(value))
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except ValueError:
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# this might not be a UUID, depending on the situation (i.e.
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# federation)
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return (False, value)
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@classmethod
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def base64_encode(cls, s):
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"""Encode a URL-safe string.
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:type s: six.text_type
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:rtype: six.text_type
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"""
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# urlsafe_b64encode() returns six.binary_type so need to convert to
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# six.text_type, might as well do it before stripping.
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return base64.urlsafe_b64encode(s).decode('utf-8').rstrip('=')
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@classmethod
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def random_urlsafe_str_to_bytes(cls, s):
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"""Convert string from :func:`random_urlsafe_str()` to six.binary_type.
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:type s: six.text_type
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:rtype: six.binary_type
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"""
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# urlsafe_b64decode() requires str, unicode isn't accepted.
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s = str(s)
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# restore the padding (==) at the end of the string
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return base64.urlsafe_b64decode(s + '==')
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