Switch to oslo.policy

Switch to the first official release of oslo.policy.

Change-Id: Ibf3bf061d41a6c3d050d4a5d562039bff734bda9
Closes-Bug: #1421863
yuntongjin 8 years ago committed by Thomas Herve
parent 547c683014
commit 4154ce7578
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  2. 962
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@ -18,16 +18,14 @@
"""Policy Engine For Heat"""
from oslo_config import cfg
from oslo_policy import policy
from heat.common import exception
from heat.openstack.common import policy
'default': policy.FalseCheck(),
DEFAULT_RULES = policy.Rules.from_dict({'default': '!'})
class Enforcer(object):
@ -39,7 +37,7 @@ class Enforcer(object):
self.exc = exc
self.default_rule = default_rule
self.enforcer = policy.Enforcer(
default_rule=default_rule, policy_file=policy_file)
CONF, default_rule=default_rule, policy_file=policy_file)
def set_rules(self, rules, overwrite=True):
"""Create a new Rules object based on the provided dict of rules."""

@ -1,962 +0,0 @@
# -*- coding: utf-8 -*-
# Copyright (c) 2012 OpenStack Foundation.
# All Rights Reserved.
# 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.
Common Policy Engine Implementation
Policies can be expressed in one of two forms: A list of lists, or a
string written in the new policy language.
In the list-of-lists representation, each check inside the innermost
list is combined as with an "and" conjunction--for that check to pass,
all the specified checks must pass. These innermost lists are then
combined as with an "or" conjunction. As an example, take the following
rule, expressed in the list-of-lists representation::
[["role:admin"], ["project_id:%(project_id)s", "role:projectadmin"]]
This is the original way of expressing policies, but there now exists a
new way: the policy language.
In the policy language, each check is specified the same way as in the
list-of-lists representation: a simple "a:b" pair that is matched to
the correct class to perform that check::
|User's Role | role:admin |
|Rules already defined on policy | rule:admin_required |
|Against URL's¹ | http://my-url.org/check |
|User attributes² | project_id:%(target.project.id)s |
|Strings | <variable>:'xpto2035abc' |
| | 'myproject':<variable> |
| | project_id:xpto2035abc |
|Literals | domain_id:20 |
| | True:%(user.enabled)s |
¹URL checking must return 'True' to be valid
²User attributes (obtained through the token): user_id, domain_id or project_id
Conjunction operators are available, allowing for more expressiveness
in crafting policies. So, in the policy language, the previous check in
list-of-lists becomes::
role:admin or (project_id:%(project_id)s and role:projectadmin)
The policy language also has the "not" operator, allowing a richer
policy rule::
project_id:%(project_id)s and not role:dunce
Attributes sent along with API calls can be used by the policy engine
(on the right side of the expression), by using the following syntax::
Contextual attributes of objects identified by their IDs are loaded
from the database. They are also available to the policy engine and
can be checked through the `target` keyword::
Finally, two special policy checks should be mentioned; the policy
check "@" will always accept an access, and the policy check "!" will
always reject an access. (Note that if a rule is either the empty
list ("[]") or the empty string, this is equivalent to the "@" policy
check.) Of these, the "!" policy check is probably the most useful,
as it allows particular rules to be explicitly disabled.
import abc
import ast
import copy
import logging
import os
import re
from oslo_config import cfg
from oslo_serialization import jsonutils
import six
import six.moves.urllib.parse as urlparse
import six.moves.urllib.request as urlrequest
from heat.openstack.common import fileutils
from heat.openstack.common._i18n import _, _LE, _LI
policy_opts = [
help=_('The JSON file that defines policies.')),
help=_('Default rule. Enforced when a requested rule is not '
help=_('Directories where policy configuration files are '
'stored. They can be relative to any directory '
'in the search path defined by the config_dir '
'option, or absolute paths. The file defined by '
'policy_file must exist for these directories to '
'be searched.')),
LOG = logging.getLogger(__name__)
_checks = {}
def list_opts():
"""Entry point for oslo.config-generator."""
return [(None, copy.deepcopy(policy_opts))]
class PolicyNotAuthorized(Exception):
def __init__(self, rule):
msg = _("Policy doesn't allow %s to be performed.") % rule
super(PolicyNotAuthorized, self).__init__(msg)
class Rules(dict):
"""A store for rules. Handles the default_rule setting directly."""
def load_json(cls, data, default_rule=None):
"""Allow loading of JSON rule data."""
# Suck in the JSON data and parse the rules
rules = dict((k, parse_rule(v)) for k, v in
return cls(rules, default_rule)
def __init__(self, rules=None, default_rule=None):
"""Initialize the Rules store."""
super(Rules, self).__init__(rules or {})
self.default_rule = default_rule
def __missing__(self, key):
"""Implements the default rule handling."""
if isinstance(self.default_rule, dict):
raise KeyError(key)
# If the default rule isn't actually defined, do something
# reasonably intelligent
if not self.default_rule:
raise KeyError(key)
if isinstance(self.default_rule, BaseCheck):
return self.default_rule
# We need to check this or we can get infinite recursion
if self.default_rule not in self:
raise KeyError(key)
elif isinstance(self.default_rule, six.string_types):
return self[self.default_rule]
def __str__(self):
"""Dumps a string representation of the rules."""
# Start by building the canonical strings for the rules
out_rules = {}
for key, value in self.items():
# Use empty string for singleton TrueCheck instances
if isinstance(value, TrueCheck):
out_rules[key] = ''
out_rules[key] = str(value)
# Dump a pretty-printed JSON representation
return jsonutils.dumps(out_rules, indent=4)
class Enforcer(object):
"""Responsible for loading and enforcing rules.
:param policy_file: Custom policy file to use, if none is
specified, `CONF.policy_file` will be
:param rules: Default dictionary / Rules to use. It will be
considered just in the first instantiation. If
`load_rules(True)`, `clear()` or `set_rules(True)`
is called this will be overwritten.
:param default_rule: Default rule to use, CONF.default_rule will
be used if none is specified.
:param use_conf: Whether to load rules from cache or config file.
:param overwrite: Whether to overwrite existing rules when reload rules
from config file.
def __init__(self, policy_file=None, rules=None,
default_rule=None, use_conf=True, overwrite=True):
self.default_rule = default_rule or CONF.policy_default_rule
self.rules = Rules(rules, self.default_rule)
self.policy_path = None
self.policy_file = policy_file or CONF.policy_file
self.use_conf = use_conf
self.overwrite = overwrite
def set_rules(self, rules, overwrite=True, use_conf=False):
"""Create a new Rules object based on the provided dict of rules.
:param rules: New rules to use. It should be an instance of dict.
:param overwrite: Whether to overwrite current rules or update them
with the new rules.
:param use_conf: Whether to reload rules from cache or config file.
if not isinstance(rules, dict):
raise TypeError(_("Rules must be an instance of dict or Rules, "
"got %s instead") % type(rules))
self.use_conf = use_conf
if overwrite:
self.rules = Rules(rules, self.default_rule)
def clear(self):
"""Clears Enforcer rules, policy's cache and policy's path."""
self.default_rule = None
self.policy_path = None
def load_rules(self, force_reload=False):
"""Loads policy_path's rules.
Policy file is cached and will be reloaded if modified.
:param force_reload: Whether to reload rules from config file.
if force_reload:
self.use_conf = force_reload
if self.use_conf:
if not self.policy_path:
self.policy_path = self._get_policy_path(self.policy_file)
self._load_policy_file(self.policy_path, force_reload,
for path in CONF.policy_dirs:
path = self._get_policy_path(path)
except cfg.ConfigFilesNotFoundError:
LOG.info(_LI("Can not find policy directory: %s"), path)
force_reload, False)
def _walk_through_policy_directory(path, func, *args):
# We do not iterate over sub-directories.
policy_files = next(os.walk(path))[2]
for policy_file in [p for p in policy_files if not p.startswith('.')]:
func(os.path.join(path, policy_file), *args)
def _load_policy_file(self, path, force_reload, overwrite=True):
reloaded, data = fileutils.read_cached_file(
path, force_reload=force_reload)
if reloaded or not self.rules or not overwrite:
rules = Rules.load_json(data, self.default_rule)
self.set_rules(rules, overwrite=overwrite, use_conf=True)
LOG.debug("Rules successfully reloaded")
def _get_policy_path(self, path):
"""Locate the policy json data file/path.
:param path: It's value can be a full path or related path. When
full path specified, this function just returns the full
path. When related path specified, this function will
search configuration directories to find one that exists.
:returns: The policy path
:raises: ConfigFilesNotFoundError if the file/path couldn't
be located.
policy_path = CONF.find_file(path)
if policy_path:
return policy_path
raise cfg.ConfigFilesNotFoundError((path,))
def enforce(self, rule, target, creds, do_raise=False,
exc=None, *args, **kwargs):
"""Checks authorization of a rule against the target and credentials.
:param rule: A string or BaseCheck instance specifying the rule
to evaluate.
:param target: As much information about the object being operated
on as possible, as a dictionary.
:param creds: As much information about the user performing the
action as possible, as a dictionary.
:param do_raise: Whether to raise an exception or not if check
:param exc: Class of the exception to raise if the check fails.
Any remaining arguments passed to enforce() (both
positional and keyword arguments) will be passed to
the exception class. If not specified, PolicyNotAuthorized
will be used.
:return: Returns False if the policy does not allow the action and
exc is not provided; otherwise, returns a value that
evaluates to True. Note: for rules using the "case"
expression, this True value will be the specified string
from the expression.
# Allow the rule to be a Check tree
if isinstance(rule, BaseCheck):
result = rule(target, creds, self)
elif not self.rules:
# No rules to reference means we're going to fail closed
result = False
# Evaluate the rule
result = self.rules[rule](target, creds, self)
except KeyError:
LOG.debug("Rule [%s] doesn't exist" % rule)
# If the rule doesn't exist, fail closed
result = False
# If it is False, raise the exception if requested
if do_raise and not result:
if exc:
raise exc(*args, **kwargs)
raise PolicyNotAuthorized(rule)
return result
class BaseCheck(object):
"""Abstract base class for Check classes."""
def __str__(self):
"""String representation of the Check tree rooted at this node."""
def __call__(self, target, cred, enforcer):
"""Triggers if instance of the class is called.
Performs the check. Returns False to reject the access or a
true value (not necessary True) to accept the access.
class FalseCheck(BaseCheck):
"""A policy check that always returns False (disallow)."""
def __str__(self):
"""Return a string representation of this check."""
return "!"
def __call__(self, target, cred, enforcer):
"""Check the policy."""
return False
class TrueCheck(BaseCheck):
"""A policy check that always returns True (allow)."""
def __str__(self):
"""Return a string representation of this check."""
return "@"
def __call__(self, target, cred, enforcer):
"""Check the policy."""
return True
class Check(BaseCheck):
"""A base class to allow for user-defined policy checks."""
def __init__(self, kind, match):
"""Initiates Check instance.
:param kind: The kind of the check, i.e., the field before the
:param match: The match of the check, i.e., the field after
the ':'.
self.kind = kind
self.match = match
def __str__(self):
"""Return a string representation of this check."""
return "%s:%s" % (self.kind, self.match)
class NotCheck(BaseCheck):
"""Implements the "not" logical operator.
A policy check that inverts the result of another policy check.
def __init__(self, rule):
"""Initialize the 'not' check.
:param rule: The rule to negate. Must be a Check.
self.rule = rule
def __str__(self):
"""Return a string representation of this check."""
return "not %s" % self.rule
def __call__(self, target, cred, enforcer):
"""Check the policy.
Returns the logical inverse of the wrapped check.
return not self.rule(target, cred, enforcer)
class AndCheck(BaseCheck):
"""Implements the "and" logical operator.
A policy check that requires that a list of other checks all return True.
def __init__(self, rules):
"""Initialize the 'and' check.
:param rules: A list of rules that will be tested.
self.rules = rules
def __str__(self):
"""Return a string representation of this check."""
return "(%s)" % ' and '.join(str(r) for r in self.rules)
def __call__(self, target, cred, enforcer):
"""Check the policy.
Requires that all rules accept in order to return True.
for rule in self.rules:
if not rule(target, cred, enforcer):
return False
return True
def add_check(self, rule):
"""Adds rule to be tested.
Allows addition of another rule to the list of rules that will
be tested. Returns the AndCheck object for convenience.
return self
class OrCheck(BaseCheck):
"""Implements the "or" operator.
A policy check that requires that at least one of a list of other
checks returns True.
def __init__(self, rules):
"""Initialize the 'or' check.
:param rules: A list of rules that will be tested.
self.rules = rules
def __str__(self):
"""Return a string representation of this check."""
return "(%s)" % ' or '.join(str(r) for r in self.rules)
def __call__(self, target, cred, enforcer):
"""Check the policy.
Requires that at least one rule accept in order to return True.
for rule in self.rules:
if rule(target, cred, enforcer):
return True
return False
def add_check(self, rule):
"""Adds rule to be tested.
Allows addition of another rule to the list of rules that will
be tested. Returns the OrCheck object for convenience.
return self
def _parse_check(rule):
"""Parse a single base check rule into an appropriate Check object."""
# Handle the special checks
if rule == '!':
return FalseCheck()
elif rule == '@':
return TrueCheck()
kind, match = rule.split(':', 1)
except Exception:
LOG.exception(_LE("Failed to understand rule %s") % rule)
# If the rule is invalid, we'll fail closed
return FalseCheck()
# Find what implements the check
if kind in _checks:
return _checks[kind](kind, match)
elif None in _checks:
return _checks[None](kind, match)
LOG.error(_LE("No handler for matches of kind %s") % kind)
return FalseCheck()
def _parse_list_rule(rule):
"""Translates the old list-of-lists syntax into a tree of Check objects.
Provided for backwards compatibility.
# Empty rule defaults to True
if not rule:
return TrueCheck()
# Outer list is joined by "or"; inner list by "and"
or_list = []
for inner_rule in rule:
# Elide empty inner lists
if not inner_rule:
# Handle bare strings
if isinstance(inner_rule, six.string_types):
inner_rule = [inner_rule]
# Parse the inner rules into Check objects
and_list = [_parse_check(r) for r in inner_rule]
# Append the appropriate check to the or_list
if len(and_list) == 1:
# If we have only one check, omit the "or"
if not or_list:
return FalseCheck()
elif len(or_list) == 1:
return or_list[0]
return OrCheck(or_list)
# Used for tokenizing the policy language
_tokenize_re = re.compile(r'\s+')
def _parse_tokenize(rule):
"""Tokenizer for the policy language.
Most of the single-character tokens are specified in the
_tokenize_re; however, parentheses need to be handled specially,
because they can appear inside a check string. Thankfully, those
parentheses that appear inside a check string can never occur at
the very beginning or end ("%(variable)s" is the correct syntax).
for tok in _tokenize_re.split(rule):
# Skip empty tokens
if not tok or tok.isspace():
# Handle leading parens on the token
clean = tok.lstrip('(')
for i in range(len(tok) - len(clean)):
yield '(', '('
# If it was only parentheses, continue
if not clean:
tok = clean
# Handle trailing parens on the token
clean = tok.rstrip(')')
trail = len(tok) - len(clean)
# Yield the cleaned token
lowered = clean.lower()
if lowered in ('and', 'or', 'not'):
# Special tokens
yield lowered, clean
elif clean:
# Not a special token, but not composed solely of ')'
if len(tok) >= 2 and ((tok[0], tok[-1]) in
[('"', '"'), ("'", "'")]):
# It's a quoted string
yield 'string', tok[1:-1]
yield 'check', _parse_check(clean)
# Yield the trailing parens
for i in range(trail):
yield ')', ')'
class ParseStateMeta(type):
"""Metaclass for the ParseState class.
Facilitates identifying reduction methods.
def __new__(mcs, name, bases, cls_dict):
"""Create the class.
Injects the 'reducers' list, a list of tuples matching token sequences
to the names of the corresponding reduction methods.
reducers = []
for key, value in cls_dict.items():
if not hasattr(value, 'reducers'):
for reduction in value.reducers:
reducers.append((reduction, key))
cls_dict['reducers'] = reducers
return super(ParseStateMeta, mcs).__new__(mcs, name, bases, cls_dict)
def reducer(*tokens):
"""Decorator for reduction methods.
Arguments are a sequence of tokens, in order, which should trigger running
this reduction method.
def decorator(func):
# Make sure we have a list of reducer sequences
if not hasattr(func, 'reducers'):
func.reducers = []
# Add the tokens to the list of reducer sequences
return func
return decorator
class ParseState(object):
"""Implement the core of parsing the policy language.
Uses a greedy reduction algorithm to reduce a sequence of tokens into
a single terminal, the value of which will be the root of the Check tree.
Note: error reporting is rather lacking. The best we can get with
this parser formulation is an overall "parse failed" error.
Fortunately, the policy language is simple enough that this
shouldn't be that big a problem.
def __init__(self):
"""Initialize the ParseState."""
self.tokens = []
self.values = []
def reduce(self):
"""Perform a greedy reduction of the token stream.
If a reducer method matches, it will be executed, then the
reduce() method will be called recursively to search for any more
possible reductions.
for reduction, methname in self.reducers:
if (len(self.tokens) >= len(reduction) and
self.tokens[-len(reduction):] == reduction):
# Get the reduction method
meth = getattr(self, methname)
# Reduce the token stream
results = meth(*self.values[-len(reduction):])
# Update the tokens and values
self.tokens[-len(reduction):] = [r[0] for r in results]
self.values[-len(reduction):] = [r[1] for r in results]
# Check for any more reductions
return self.reduce()
def shift(self, tok, value):
"""Adds one more token to the state. Calls reduce()."""
# Do a greedy reduce...
def result(self):
"""Obtain the final result of the parse.
Raises ValueError if the parse failed to reduce to a single result.
if len(self.values) != 1:
raise ValueError("Could not parse rule")
return self.values[0]
@reducer('(', 'check', ')')
@reducer('(', 'and_expr', ')')
@reducer('(', 'or_expr', ')')
def _wrap_check(self, _p1, check, _p2):
"""Turn parenthesized expressions into a 'check' token."""
return [('check', check)]
@reducer('check', 'and', 'check')
def _make_and_expr(self, check1, _and, check2):
"""Create an 'and_expr'.
Join two checks by the 'and' operator.
return [('and_expr', AndCheck([check1, check2]))]
@reducer('and_expr', 'and', 'check')
def _extend_and_expr(self, and_expr, _and, check):
"""Extend an 'and_expr' by adding one more check."""
return [('and_expr', and_expr.add_check(check))]
@reducer('check', 'or', 'check')
def _make_or_expr(self, check1, _or, check2):
"""Create an 'or_expr'.
Join two checks by the 'or' operator.
return [('or_expr', OrCheck([check1, check2]))]
@reducer('or_expr', 'or', 'check')
def _extend_or_expr(self, or_expr, _or, check):
"""Extend an 'or_expr' by adding one more check."""
return [('or_expr', or_expr.add_check(check))]
@reducer('not', 'check')
def _make_not_expr(self, _not, check):
"""Invert the result of another check."""
return [('check', NotCheck(check))]
def _parse_text_rule(rule):
"""Parses policy to the tree.
Translates a policy written in the policy language into a tree of
Check objects.
# Empty rule means always accept
if not rule:
return TrueCheck()
# Parse the token stream
state = ParseState()
for tok, value in _parse_tokenize(rule):
state.shift(tok, value)
return state.result
except ValueError:
# Couldn't parse the rule
LOG.exception(_LE("Failed to understand rule %s") % rule)
# Fail closed
return FalseCheck()
def parse_rule(rule):
"""Parses a policy rule into a tree of Check objects."""
# If the rule is a string, it's in the policy language
if isinstance(rule, six.string_types):
return _parse_text_rule(rule)
return _parse_list_rule(rule)
def register(name, func=None):
"""Register a function or Check class as a policy check.
:param name: Gives the name of the check type, e.g., 'rule',
'role', etc. If name is None, a default check type
will be registered.
:param func: If given, provides the function or class to register.
If not given, returns a function taking one argument
to specify the function or class to register,
allowing use as a decorator.
# Perform the actual decoration by registering the function or
# class. Returns the function or class for compliance with the
# decorator interface.
def decorator(func):
_checks[name] = func
return func
# If the function or class is given, do the registration
if func:
return decorator(func)
return decorator
class RuleCheck(Check):
def __call__(self, target, creds, enforcer):
"""Recursively checks credentials based on the defined rules."""
return enforcer.rules[self.match](target, creds, enforcer)
except KeyError:
# We don't have any matching rule; fail closed
return False
class RoleCheck(Check):
def __call__(self, target, creds, enforcer):
"""Check that there is a matching role in the cred dict."""
return self.match.lower() in [x.lower() for x in creds['roles']]
class HttpCheck(Check):
def __call__(self, target, creds, enforcer):
"""Check http: rules by calling to a remote server.
This example implementation simply verifies that the response
is exactly 'True'.
url = ('http:' + self.match) % target
# Convert instances of object() in target temporarily to
# empty dict to avoid circular reference detection
# errors in jsonutils.dumps().
temp_target = copy.deepcopy(target)
for key in six.iterkeys(target):
element = target.get(key)
if type(element) is object:
temp_target[key] = {}
data = {'target': jsonutils.dumps(temp_target),
'credentials': jsonutils.dumps(creds)}
post_data = urlparse.urlencode(data)
f = urlrequest.urlopen(url, post_data)
return f.read() == "True"
class GenericCheck(Check):
def __call__(self, target, creds, enforcer):
"""Check an individual match.
Matches look like:
match = self.match % target
except KeyError:
# While doing GenericCheck if key not
# present in Target return false
return False
# Try to interpret self.kind as a literal
leftval = ast.literal_eval(self.kind)
except ValueError:
kind_parts = self.kind.split('.')
leftval = creds
for kind_part in kind_parts:
leftval = leftval[kind_part]
except KeyError:
return False
return match == six.text_type(leftval)

@ -16,6 +16,7 @@ import os
import mock
from oslo_config import cfg
from oslo_middleware import request_id
from oslo_policy import opts as policy_opts
import webob
from heat.common import context
@ -247,7 +248,7 @@ class RequestContextMiddlewareTest(common.HeatTestCase):
cfg.StrOpt('project', default='heat'),
cfg.CONF.set_override('policy_file', 'check_admin.json')
policy_opts.set_defaults(cfg.CONF, 'check_admin.json')
def test_context_middleware(self):

@ -17,10 +17,10 @@
import os.path
from oslo_config import cfg
from oslo_policy import policy as base_policy
from heat.common import exception
from heat.common import policy
from heat.openstack.common import policy as base_policy
from heat.tests import common
from heat.tests import utils
@ -155,11 +155,10 @@ class TestPolicyEnforcer(common.HeatTestCase):
def test_default_rule(self):
ctx = utils.dummy_context(roles=['not_a_stack_user'])
default_rule = base_policy.FalseCheck()
enforcer = policy.Enforcer(
exc=None, default_rule=default_rule)
exc=None, default_rule='!')
action = 'no_such_action'
self.assertFalse(enforcer.enforce(ctx, action))

@ -4,7 +4,6 @@

@ -20,6 +20,7 @@ oslo.i18n>=1.5.0 # Apache-2.0
oslo.log>=1.0.0 # Apache-2.0
oslo.messaging>=1.8.0 # Apache-2.0
oslo.middleware>=1.2.0 # Apache-2.0
oslo.policy>=0.3.1 # Apache-2.0
oslo.serialization>=1.4.0 # Apache-2.0
oslo.utils>=1.4.0 # Apache-2.0
osprofiler>=0.3.0 # Apache-2.0