87d644675e
This change is going to upgrade ranger to use Python 3.x Change-Id: I563661e071c56c2df7e0e1a6e365aecd4158b6cd
533 lines
19 KiB
Python
Executable File
533 lines
19 KiB
Python
Executable File
# -*- coding: utf-8 -*-
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#
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# Copyright (c) 2012 OpenStack Foundation.
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# All Rights Reserved.
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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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"""
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Common Policy Engine Implementation
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Policies are expressed as a target and an associated rule::
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"<target>": <rule>
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The `target` is specific to the service that is conducting policy
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enforcement. Typically, the target refers to an API call.
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For the `<rule>` part, see `Policy Rule Expressions`.
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Policy Rule Expressions
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~~~~~~~~~~~~~~~~~~~~~~~
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Policy rules can be expressed in one of two forms: a string written in the new
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policy language or a list of lists. The string format is preferred since it's
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easier for most people to understand.
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In the policy language, each check is specified as a simple "a:b" pair that is
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matched to the correct class to perform that check:
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+--------------------------------+------------------------------------------+
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| TYPE | SYNTAX |
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+================================+==========================================+
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|User's Role | role:admin |
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+--------------------------------+------------------------------------------+
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|Rules already defined on policy | rule:admin_required |
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+--------------------------------+------------------------------------------+
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|Against URLs¹ | http://my-url.org/check |
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+--------------------------------+------------------------------------------+
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|User attributes² | project_id:%(target.project.id)s |
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+--------------------------------+------------------------------------------+
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|Strings | - <variable>:'xpto2035abc' |
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| | - 'myproject':<variable> |
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+--------------------------------+------------------------------------------+
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| | - project_id:xpto2035abc |
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|Literals | - domain_id:20 |
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| | - True:%(user.enabled)s |
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+--------------------------------+------------------------------------------+
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¹URL checking must return ``True`` to be valid
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²User attributes (obtained through the token): user_id, domain_id or project_id
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Conjunction operators ``and`` and ``or`` are available, allowing for more
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expressiveness in crafting policies. For example::
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"role:admin or (project_id:%(project_id)s and role:projectadmin)"
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The policy language also has the ``not`` operator, allowing a richer
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policy rule::
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"project_id:%(project_id)s and not role:dunce"
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Operator precedence is below:
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+------------+-------------+-------------+
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| PRECEDENCE | TYPE | EXPRESSION |
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+============+=============+=============+
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| 4 | Grouping | (...) |
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+------------+-------------+-------------+
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| 3 | Logical NOT | not ... |
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+------------+-------------+-------------+
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| 2 | Logical AND | ... and ... |
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+------------+-------------+-------------+
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| 1 | Logical OR | ... or ... |
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+------------+-------------+-------------+
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Operator with larger precedence number precedes others with smaller numbers.
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In the list-of-lists representation, each check inside the innermost
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list is combined as with an "and" conjunction -- for that check to pass,
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all the specified checks must pass. These innermost lists are then
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combined as with an "or" conjunction. As an example, take the following
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rule, expressed in the list-of-lists representation::
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[["role:admin"], ["project_id:%(project_id)s", "role:projectadmin"]]
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Finally, two special policy checks should be mentioned; the policy
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check "@" will always accept an access, and the policy check "!" will
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always reject an access. (Note that if a rule is either the empty
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list (``[]``) or the empty string (``""``), this is equivalent to the "@"
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policy check.) Of these, the "!" policy check is probably the most useful,
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as it allows particular rules to be explicitly disabled.
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Generic Checks
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~~~~~~~~~~~~~~
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A `generic` check is used to perform matching against attributes that are sent
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along with the API calls. These attributes can be used by the policy engine
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(on the right side of the expression), by using the following syntax::
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<some_attribute>:%(user.id)s
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The value on the right-hand side is either a string or resolves to a
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string using regular Python string substitution. The available attributes
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and values are dependent on the program that is using the common policy
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engine.
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All of these attributes (related to users, API calls, and context) can be
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checked against each other or against constants. It is important to note
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that these attributes are specific to the service that is conducting
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policy enforcement.
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Generic checks can be used to perform policy checks on the following user
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attributes obtained through a token:
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- user_id
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- domain_id or project_id (depending on the token scope)
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- list of roles held for the given token scope
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For example, a check on the user_id would be defined as::
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user_id:<some_value>
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Together with the previously shown example, a complete generic check
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would be::
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user_id:%(user.id)s
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It is also possible to perform checks against other attributes that
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represent the credentials. This is done by adding additional values to
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the ``creds`` dict that is passed to the
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:meth:`~oslo_policy.policy.Enforcer.enforce` method.
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Special Checks
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~~~~~~~~~~~~~~
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Special checks allow for more flexibility than is possible using generic
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checks. The built-in special check types are ``role``, ``rule``, and ``http``
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checks.
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Role Check
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^^^^^^^^^^
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A ``role`` check is used to check if a specific role is present in the supplied
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credentials. A role check is expressed as::
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"role:<role_name>"
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Rule Check
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^^^^^^^^^^
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A :class:`rule check <oslo_policy.policy.RuleCheck>` is used to
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reference another defined rule by its name. This allows for common
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checks to be defined once as a reusable rule, which is then referenced
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within other rules. It also allows one to define a set of checks as a
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more descriptive name to aid in readability of policy. A rule check is
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expressed as::
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"rule:<rule_name>"
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The following example shows a role check that is defined as a rule,
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which is then used via a rule check::
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"admin_required": "role:admin"
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"<target>": "rule:admin_required"
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HTTP Check
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^^^^^^^^^^
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An ``http`` check is used to make an HTTP request to a remote server to
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determine the results of the check. The target and credentials are passed to
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the remote server for evaluation. The action is authorized if the remote
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server returns a response of ``True``. An http check is expressed as::
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"http:<target URI>"
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It is expected that the target URI contains a string formatting keyword,
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where the keyword is a key from the target dictionary. An example of an
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http check where the `name` key from the target is used to construct the
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URL is would be defined as::
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"http://server.test/%(name)s"
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Registering New Special Checks
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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It is also possible for additional special check types to be registered
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using the :func:`~oslo_policy.policy.register` function.
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The following classes can be used as parents for custom special check types:
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* :class:`~oslo_policy.policy.AndCheck`
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* :class:`~oslo_policy.policy.NotCheck`
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* :class:`~oslo_policy.policy.OrCheck`
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* :class:`~oslo_policy.policy.RuleCheck`
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Default Rule
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~~~~~~~~~~~~
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A default rule can be defined, which will be enforced when a rule does
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not exist for the target that is being checked. By default, the rule
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associated with the rule name of ``default`` will be used as the default
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rule. It is possible to use a different rule name as the default rule
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by setting the ``policy_default_rule`` configuration setting to the
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desired rule name.
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"""
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import logging
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import os
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from . import _parser
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from orm.common.orm_common.utils import api_error_utils as err_utils
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from oslo_config import cfg
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from oslo_policy import _checks
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from oslo_policy._i18n import _
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from oslo_serialization import jsonutils
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import six
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LOG = logging.getLogger(__name__)
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register = _checks.register
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"""Register a function or :class:`.Check` class as a policy check.
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:param name: Gives the name of the check type, e.g., "rule",
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"role", etc. If name is ``None``, a default check type
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will be registered.
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:param func: If given, provides the function or class to register.
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If not given, returns a function taking one argument
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to specify the function or class to register,
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allowing use as a decorator.
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"""
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Check = _checks.Check
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"""A base class to allow for user-defined policy checks.
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:param kind: The kind of the check, i.e., the field before the ``:``.
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:param match: The match of the check, i.e., the field after the ``:``.
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"""
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AndCheck = _checks.AndCheck
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"""Implements the "and" logical operator.
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A policy check that requires that a list of other checks all return True.
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:param list rules: rules that will be tested.
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"""
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NotCheck = _checks.NotCheck
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"""Implements the "not" logical operator.
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A policy check that inverts the result of another policy check.
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:param rule: The rule to negate.
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:type rule: oslo_policy.policy.Check
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"""
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OrCheck = _checks.OrCheck
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"""Implements the "or" operator.
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A policy check that requires that at least one of a list of other
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checks returns ``True``.
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:param rules: A list of rules that will be tested.
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"""
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RuleCheck = _checks.RuleCheck
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"""Recursively checks credentials based on the defined rules."""
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class PolicyNotAuthorized(Exception):
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"""Default exception raised for policy enforcement failure."""
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def __init__(self, rule, target, creds):
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msg = (_('%(rule)s on %(target)s by %(creds)s disallowed by policy') %
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{'rule': rule, 'target': target, 'creds': creds})
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super(PolicyNotAuthorized, self).__init__(msg)
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class Rules(dict):
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"""A store for rules. Handles the default_rule setting directly."""
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@classmethod
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def load_json(cls, data, default_rule=None):
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"""Allow loading of JSON rule data."""
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# Suck in the JSON data and parse the rules
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rules = {k: _parser.parse_rule(v)
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for k, v in list(jsonutils.loads(data).items())}
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return cls(rules, default_rule)
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@classmethod
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def from_dict(cls, rules_dict, default_rule=None):
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"""Allow loading of rule data from a dictionary."""
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# Parse the rules stored in the dictionary
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rules = {k: _parser.parse_rule(v) for k, v in list(rules_dict.items())}
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return cls(rules, default_rule)
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def __init__(self, rules=None, default_rule=None):
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"""Initialize the Rules store."""
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super(Rules, self).__init__(rules or {})
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self.default_rule = default_rule
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def __missing__(self, key):
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"""Implements the default rule handling."""
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if isinstance(self.default_rule, dict):
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raise KeyError(key)
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# If the default rule isn't actually defined, do something
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# reasonably intelligent
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if not self.default_rule:
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raise KeyError(key)
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if isinstance(self.default_rule, _checks.BaseCheck):
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return self.default_rule
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# We need to check this or we can get infinite recursion
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if self.default_rule not in self:
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raise KeyError(key)
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elif isinstance(self.default_rule, six.string_types):
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return self[self.default_rule]
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def __str__(self):
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"""Dumps a string representation of the rules."""
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# Start by building the canonical strings for the rules
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out_rules = {}
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for key, value in list(self.items()):
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# Use empty string for singleton TrueCheck instances
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if isinstance(value, _checks.TrueCheck):
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out_rules[key] = ''
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else:
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out_rules[key] = str(value)
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# Dump a pretty-printed JSON representation
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return jsonutils.dumps(out_rules, indent=4)
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class Enforcer(object):
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"""Responsible for loading and enforcing rules.
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:param conf: A configuration object.
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:param policy_file: Custom policy file to use, if none is
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specified, ``conf.oslo_policy.policy_file`` will be
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used.
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:param rules: Default dictionary / Rules to use. It will be
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considered just in the first instantiation. If
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:meth:`load_rules` with ``force_reload=True``,
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:meth:`clear` or :meth:`set_rules` with ``overwrite=True``
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is called this will be overwritten.
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:param default_rule: Default rule to use, conf.default_rule will
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be used if none is specified.
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:param use_conf: Whether to load rules from cache or config file.
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:param overwrite: Whether to overwrite existing rules when reload rules
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from config file.
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"""
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def __init__(self, conf, policy_file=None, rules=None,
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default_rule=None, use_conf=True, overwrite=True):
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self.conf = conf
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self.default_rule = default_rule or '!'
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self.rules = Rules(rules, self.default_rule)
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self.policy_path = None
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self.policy_file = policy_file
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self.use_conf = use_conf
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self.overwrite = overwrite
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self._loaded_files = []
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self._policy_dir_mtimes = {}
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self._file_cache = {}
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def set_rules(self, rules, overwrite=True, use_conf=False):
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"""Create a new :class:`Rules` based on the provided dict of rules.
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:param dict rules: New rules to use.
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:param overwrite: Whether to overwrite current rules or update them
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with the new rules.
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:param use_conf: Whether to reload rules from cache or config file.
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"""
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if not isinstance(rules, dict):
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raise TypeError(_('Rules must be an instance of dict or Rules, '
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'got %s instead') % type(rules))
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self.use_conf = use_conf
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if overwrite:
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self.rules = Rules(rules, self.default_rule)
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else:
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self.rules.update(rules)
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def clear(self):
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"""Clears :class:`Enforcer` contents.
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This will clear this instances rules, policy's cache, file cache
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and policy's path.
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"""
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self.set_rules({})
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self.default_rule = None
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self.policy_path = None
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self._loaded_files = []
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self._policy_dir_mtimes = {}
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self._file_cache.clear()
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def load_rules(self, force_reload=False):
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"""Loads policy_path's rules.
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Policy file is cached and will be reloaded if modified.
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:param force_reload: Whether to reload rules from config file.
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"""
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if force_reload:
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self.use_conf = force_reload
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@staticmethod
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def _is_directory_updated(cache, path):
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# Get the current modified time and compare it to what is in
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# the cache and check if the new mtime is greater than what
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# is in the cache
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mtime = 0
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if os.path.exists(path):
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# Make a list of all the files
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files = [path] + [os.path.join(path, file) for file in
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os.listdir(path)]
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# Pick the newest one, let's use its time.
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mtime = os.path.getmtime(max(files, key=os.path.getmtime))
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cache_info = cache.setdefault(path, {})
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if mtime > cache_info.get('mtime', 0):
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cache_info['mtime'] = mtime
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return True
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return False
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@staticmethod
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def _walk_through_policy_directory(path, func, *args):
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if not os.path.isdir(path):
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raise ValueError('%s is not a directory' % path)
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# We do not iterate over sub-directories.
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policy_files = next(os.walk(path))[2]
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policy_files.sort()
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for policy_file in [p for p in policy_files if not p.startswith('.')]:
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func(os.path.join(path, policy_file), *args)
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def _get_policy_path(self, path):
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"""Locate the policy JSON data file/path.
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:param path: It's value can be a full path or related path. When
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full path specified, this function just returns the full
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path. When related path specified, this function will
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search configuration directories to find one that exists.
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:returns: The policy path
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:raises: ConfigFilesNotFoundError if the file/path couldn't
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be located.
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"""
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policy_path = self.conf.find_file(path)
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if policy_path:
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return policy_path
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raise cfg.ConfigFilesNotFoundError((path,))
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def enforce(self, rule, target, creds, do_raise=False,
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exc=None, *args, **kwargs):
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"""Checks authorization of a rule against the target and credentials.
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:param rule: The rule to evaluate.
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:type rule: string or :class:`BaseCheck`
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:param dict target: As much information about the object being operated
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on as possible.
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:param dict creds: As much information about the user performing the
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action as possible.
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:param do_raise: Whether to raise an exception or not if check
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fails.
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:param exc: Class of the exception to raise if the check fails.
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Any remaining arguments passed to :meth:`enforce` (both
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positional and keyword arguments) will be passed to
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the exception class. If not specified,
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:class:`PolicyNotAuthorized` will be used.
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:return: ``False`` if the policy does not allow the action and `exc` is
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not provided; otherwise, returns a value that evaluates to
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``True``. Note: for rules using the "case" expression, this
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``True`` value will be the specified string from the
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expression.
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"""
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self.load_rules()
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# Allow the rule to be a Check tree
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if isinstance(rule, _checks.BaseCheck):
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result = rule(target, creds, self)
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elif not self.rules:
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# No rules to reference means we're going to fail closed
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result = False
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else:
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try:
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# Evaluate the rule
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result = self.rules[rule](target, creds, self)
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except KeyError:
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LOG.debug('Rule [%s] does not exist', rule)
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# If the rule doesn't exist, fail closed
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result = False
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# If it is False, raise the exception if requested
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if do_raise and not result:
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raise err_utils.get_error('N/A', status_code=403)
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return result
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