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