From f3c5ccf9ec190c22ce12d23bbc3b98d923e7708c Mon Sep 17 00:00:00 2001 From: Kiall Mac Innes Date: Wed, 24 Oct 2012 19:38:44 +0100 Subject: [PATCH] Policy implementation (part 1) --- etc/policy.json | 6 + moniker/central/service.py | 3 + moniker/openstack/common/policy.py | 779 +++++++++++++++++++++++++++++ moniker/policy.py | 43 ++ openstack-common.conf | 2 +- 5 files changed, 832 insertions(+), 1 deletion(-) create mode 100644 etc/policy.json create mode 100644 moniker/openstack/common/policy.py create mode 100644 moniker/policy.py diff --git a/etc/policy.json b/etc/policy.json new file mode 100644 index 000000000..9bf33832d --- /dev/null +++ b/etc/policy.json @@ -0,0 +1,6 @@ +{ + "admin": "role:admin or is_admin:True", + "admin_or_owner": "rule:admin or tenant:%(tenant)s", + + "default": "@" +} diff --git a/moniker/central/service.py b/moniker/central/service.py index c275843cd..8332576a6 100644 --- a/moniker/central/service.py +++ b/moniker/central/service.py @@ -18,6 +18,7 @@ from moniker.openstack.common import log as logging from moniker.openstack.common.rpc import service as rpc_service from moniker import database from moniker import utils +from moniker import policy from moniker.agent import api as agent_api @@ -31,6 +32,8 @@ class Service(rpc_service.Service): topic=cfg.CONF.central_topic ) + policy.init_policy() + super(Service, self).__init__(*args, **kwargs) self.init_database() diff --git a/moniker/openstack/common/policy.py b/moniker/openstack/common/policy.py new file mode 100644 index 000000000..d8791496b --- /dev/null +++ b/moniker/openstack/common/policy.py @@ -0,0 +1,779 @@ +# vim: tabstop=4 shiftwidth=4 softtabstop=4 + +# Copyright (c) 2012 OpenStack, LLC. +# 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. 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 code to perform that check. However, conjunction +operators are available, allowing for more expressiveness in crafting +policies. + +As an example, take the following rule, expressed in the list-of-lists +representation:: + + [["role:admin"], ["project_id:%(project_id)s", "role:projectadmin"]] + +In the policy language, this 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 + +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 logging +import re +import urllib + +import urllib2 + +from moniker.openstack.common.gettextutils import _ +from moniker.openstack.common import jsonutils + + +LOG = logging.getLogger(__name__) + + +_rules = None +_checks = {} + + +class Rules(dict): + """ + A store for rules. Handles the default_rule setting directly. + """ + + @classmethod + 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 + jsonutils.loads(data).items()) + + 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 the default rule isn't actually defined, do something + # reasonably intelligent + if not self.default_rule or self.default_rule not in self: + raise KeyError(key) + + 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] = '' + else: + out_rules[key] = str(value) + + # Dump a pretty-printed JSON representation + return jsonutils.dumps(out_rules, indent=4) + + +# Really have to figure out a way to deprecate this +def set_rules(rules): + """Set the rules in use for policy checks.""" + + global _rules + + _rules = rules + + +# Ditto +def reset(): + """Clear the rules used for policy checks.""" + + global _rules + + _rules = None + + +def check(rule, target, creds, exc=None, *args, **kwargs): + """ + Checks authorization of a rule against the target and credentials. + + :param rule: 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 exc: Class of the exception to raise if the check fails. + Any remaining arguments passed to check() (both + positional and keyword arguments) will be passed to + the exception class. If exc is not provided, returns + False. + + :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) + elif not _rules: + # No rules to reference means we're going to fail closed + result = False + else: + try: + # Evaluate the rule + result = _rules[rule](target, creds) + except KeyError: + # If the rule doesn't exist, fail closed + result = False + + # If it is False, raise the exception if requested + if exc and result is False: + raise exc(*args, **kwargs) + + return result + + +class BaseCheck(object): + """ + Abstract base class for Check classes. + """ + + __metaclass__ = abc.ABCMeta + + @abc.abstractmethod + def __str__(self): + """ + Retrieve a string representation of the Check tree rooted at + this node. + """ + + pass + + @abc.abstractmethod + def __call__(self, target, cred): + """ + Perform the check. Returns False to reject the access or a + true value (not necessary True) to accept the access. + """ + + pass + + +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): + """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): + """Check the policy.""" + + return True + + +class Check(BaseCheck): + """ + A base class to allow for user-defined policy checks. + """ + + def __init__(self, kind, match): + """ + :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): + """ + A policy check that inverts the result of another policy check. + Implements the "not" operator. + """ + + 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): + """ + Check the policy. Returns the logical inverse of the wrapped + check. + """ + + return not self.rule(target, cred) + + +class AndCheck(BaseCheck): + """ + A policy check that requires that a list of other checks all + return True. Implements the "and" operator. + """ + + 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): + """ + Check the policy. Requires that all rules accept in order to + return True. + """ + + for rule in self.rules: + if not rule(target, cred): + return False + + return True + + def add_check(self, rule): + """ + Allows addition of another rule to the list of rules that will + be tested. Returns the AndCheck object for convenience. + """ + + self.rules.append(rule) + return self + + +class OrCheck(BaseCheck): + """ + A policy check that requires that at least one of a list of other + checks returns True. Implements the "or" operator. + """ + + 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): + """ + Check the policy. Requires that at least one rule accept in + order to return True. + """ + + for rule in self.rules: + if rule(target, cred): + return True + + return False + + def add_check(self, rule): + """ + Allows addition of another rule to the list of rules that will + be tested. Returns the OrCheck object for convenience. + """ + + self.rules.append(rule) + 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() + + try: + kind, match = rule.split(':', 1) + except Exception: + LOG.exception(_("Failed to understand rule %(rule)s") % locals()) + # 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) + else: + LOG.error(_("No handler for matches of kind %s") % kind) + return FalseCheck() + + +def _parse_list_rule(rule): + """ + Provided for backwards compatibility. Translates the old + list-of-lists syntax into a tree of Check objects. + """ + + # 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: + continue + + # Handle bare strings + if isinstance(inner_rule, basestring): + 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: + or_list.append(and_list[0]) + else: + or_list.append(AndCheck(and_list)) + + # If we have only one check, omit the "or" + if len(or_list) == 0: + 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(): + continue + + # 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: + continue + else: + 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] + else: + 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'): + continue + 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 + func.reducers.append(list(tokens)) + + 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. + """ + + __metaclass__ = ParseStateMeta + + 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().""" + + self.tokens.append(tok) + self.values.append(value) + + # Do a greedy reduce... + self.reduce() + + @property + 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' from two checks joined 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' from two checks joined 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): + """ + 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) + + try: + return state.result + except ValueError: + # Couldn't parse the rule + LOG.exception(_("Failed to understand rule %(rule)r") % locals()) + + # 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, basestring): + 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 + + +@register("rule") +class RuleCheck(Check): + def __call__(self, target, creds): + """ + Recursively checks credentials based on the defined rules. + """ + + try: + return _rules[self.match](target, creds) + except KeyError: + # We don't have any matching rule; fail closed + return False + + +@register("role") +class RoleCheck(Check): + def __call__(self, target, creds): + """Check that there is a matching role in the cred dict.""" + + return self.match.lower() in [x.lower() for x in creds['roles']] + + +@register('http') +class HttpCheck(Check): + def __call__(self, target, creds): + """ + 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 + data = {'target': jsonutils.dumps(target), + 'credentials': jsonutils.dumps(creds)} + post_data = urllib.urlencode(data) + f = urllib2.urlopen(url, post_data) + return f.read() == "True" + + +@register(None) +class GenericCheck(Check): + def __call__(self, target, creds): + """ + Check an individual match. + + Matches look like: + + tenant:%(tenant_id)s + role:compute:admin + """ + + # TODO(termie): do dict inspection via dot syntax + match = self.match % target + if self.kind in creds: + return match == unicode(creds[self.kind]) + return False diff --git a/moniker/policy.py b/moniker/policy.py new file mode 100644 index 000000000..3e78de46c --- /dev/null +++ b/moniker/policy.py @@ -0,0 +1,43 @@ +# Copyright 2012 Managed I.T. +# +# Author: Kiall Mac Innes +# +# 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. +from moniker.openstack.common import cfg +from moniker.openstack.common import log as logging +from moniker.openstack.common import policy +from moniker import utils +from moniker import exceptions + +LOG = logging.getLogger(__name__) + +cfg.CONF.register_opts([ + cfg.StrOpt('policy-file', default='policy.json'), + cfg.StrOpt('policy-default-rule', default='default'), +]) + + +def init_policy(): + LOG.info('Initializing Policy') + + with open(utils.find_config(cfg.CONF.policy_file)) as fh: + policy_json = fh.read() + + rules = policy.Rules.load_json(policy_json, cfg.CONF.policy_default_rule) + policy.set_rules(rules) + + +def check(rule, ctxt, target={}, exc=exceptions.Forbidden): + creds = ctxt.to_dict() + + return policy.check(rule, target, creds, exc) diff --git a/openstack-common.conf b/openstack-common.conf index 3728177f0..ead6252bf 100644 --- a/openstack-common.conf +++ b/openstack-common.conf @@ -1,3 +1,3 @@ [DEFAULT] -modules=cfg,iniparser,rpc,importutils,excutils,local,jsonutils,gettextutils,timeutils,notifier,context,log,service,eventlet_backdoor,network_utils,threadgroup,loopingcall,utils,exception,setup,wsgi +modules=cfg,iniparser,rpc,importutils,excutils,local,jsonutils,gettextutils,timeutils,notifier,context,log,service,eventlet_backdoor,network_utils,threadgroup,loopingcall,utils,exception,setup,wsgi,policy base=moniker