Common-ize policies.

Both Glance and Nova make use of (almost) the same policy system,
defined in glance/common/policy.py and nova/common/policy.py,
respectively.  They also have independent glue code
(glance/api/policy.py and nova/policy.py), so that the common
policy system is substantially similar.  This makes policies a
perfect candidate for incorporation into openstack-common,
particularly given that this same code will soon be used by
Quantum.

This change adds the common policy module (along with some minor
interface changes and bug fixes) to openstack-common, along with
a test suite.

Change-Id: I0022a91f16ded28f9dc6b4975ef1b6e4cc8460ac

2 files changed, 639 insertions, 0 deletions

diff --git a/openstack/common/policy.py b/openstack/common/policy.py
new file mode 100644
index 0000000..203995a
--- /dev/null
+++ b/openstack/common/policy.py
@@ -0,0 +1,238 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright (c) 2011 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"""
+
+import json
+import logging
+import urllib
+import urllib2
+
+
+LOG = logging.getLogger(__name__)
+
+
+_BRAIN = None
+
+
+def set_brain(brain):
+    """Set the brain used by enforce().
+
+    Defaults use Brain() if not set.
+
+    """
+    global _BRAIN
+    _BRAIN = brain
+
+
+def reset():
+    """Clear the brain used by enforce()."""
+    global _BRAIN
+    _BRAIN = None
+
+
+def enforce(match_list, target_dict, credentials_dict, exc=None,
+            *args, **kwargs):
+    """Enforces authorization of some rules against credentials.
+
+    :param match_list: nested tuples of data to match against
+
+        The basic brain supports three types of match lists:
+
+            1) rules
+
+                looks like: ``('rule:compute:get_instance',)``
+
+                Retrieves the named rule from the rules dict and recursively
+                checks against the contents of the rule.
+
+            2) roles
+
+                looks like: ``('role:compute:admin',)``
+
+                Matches if the specified role is in credentials_dict['roles'].
+
+            3) generic
+
+                looks like: ``('tenant_id:%(tenant_id)s',)``
+
+                Substitutes values from the target dict into the match using
+                the % operator and matches them against the creds dict.
+
+        Combining rules:
+
+            The brain returns True if any of the outer tuple of rules
+            match and also True if all of the inner tuples match. You
+            can use this to perform simple boolean logic.  For
+            example, the following rule would return True if the creds
+            contain the role 'admin' OR the if the tenant_id matches
+            the target dict AND the the creds contains the role
+            'compute_sysadmin':
+
+            ::
+
+                {
+                    "rule:combined": (
+                        'role:admin',
+                        ('tenant_id:%(tenant_id)s', 'role:compute_sysadmin')
+                    )
+                }
+
+        Note that rule and role are reserved words in the credentials match, so
+        you can't match against properties with those names. Custom brains may
+        also add new reserved words. For example, the HttpBrain adds http as a
+        reserved word.
+
+    :param target_dict: dict of object properties
+
+      Target dicts contain as much information as we can about the object being
+      operated on.
+
+    :param credentials_dict: dict of actor properties
+
+      Credentials dicts contain as much information as we can about the user
+      performing the action.
+
+    :param exc: exception to raise
+
+      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 exc is not provided, returns
+      False.
+
+    :return: True if the policy allows the action
+    :return: False if the policy does not allow the action and exc is not set
+    """
+    global _BRAIN
+    if not _BRAIN:
+        _BRAIN = Brain()
+    if not _BRAIN.check(match_list, target_dict, credentials_dict):
+        if exc:
+            raise exc(*args, **kwargs)
+        return False
+    return True
+
+
+class Brain(object):
+    """Implements policy checking."""
+    @classmethod
+    def load_json(cls, data, default_rule=None):
+        """Init a brain using json instead of a rules dictionary."""
+        rules_dict = json.loads(data)
+        return cls(rules=rules_dict, default_rule=default_rule)
+
+    def __init__(self, rules=None, default_rule=None):
+        self.rules = rules or {}
+        self.default_rule = default_rule
+
+    def add_rule(self, key, match):
+        self.rules[key] = match
+
+    def _check(self, match, target_dict, cred_dict):
+        try:
+            match_kind, match_value = match.split(':', 1)
+        except Exception:
+            LOG.exception(_("Failed to understand rule %(match)r") % locals())
+            # If the rule is invalid, fail closed
+            return False
+        try:
+            f = getattr(self, '_check_%s' % match_kind)
+        except AttributeError:
+            if not self._check_generic(match, target_dict, cred_dict):
+                return False
+        else:
+            if not f(match_value, target_dict, cred_dict):
+                return False
+        return True
+
+    def check(self, match_list, target_dict, cred_dict):
+        """Checks authorization of some rules against credentials.
+
+        Detailed description of the check with examples in policy.enforce().
+
+        :param match_list: nested tuples of data to match against
+        :param target_dict: dict of object properties
+        :param credentials_dict: dict of actor properties
+
+        :returns: True if the check passes
+
+        """
+        if not match_list:
+            return True
+        for and_list in match_list:
+            if isinstance(and_list, basestring):
+                and_list = (and_list,)
+            if all([self._check(item, target_dict, cred_dict)
+                    for item in and_list]):
+                return True
+        return False
+
+    def _check_rule(self, match, target_dict, cred_dict):
+        """Recursively checks credentials based on the brains rules."""
+        try:
+            new_match_list = self.rules[match]
+        except KeyError:
+            if self.default_rule and match != self.default_rule:
+                new_match_list = ('rule:%s' % self.default_rule,)
+            else:
+                return False
+
+        return self.check(new_match_list, target_dict, cred_dict)
+
+    def _check_role(self, match, target_dict, cred_dict):
+        """Check that there is a matching role in the cred dict."""
+        return match.lower() in [x.lower() for x in cred_dict['roles']]
+
+    def _check_generic(self, match, target_dict, cred_dict):
+        """Check an individual match.
+
+        Matches look like:
+
+            tenant:%(tenant_id)s
+            role:compute:admin
+
+        """
+
+        # TODO(termie): do dict inspection via dot syntax
+        match = match % target_dict
+        key, value = match.split(':', 1)
+        if key in cred_dict:
+            return value == cred_dict[key]
+        return False
+
+
+class HttpBrain(Brain):
+    """A brain that can check external urls for policy.
+
+    Posts json blobs for target and credentials.
+
+    """
+
+    def _check_http(self, match, target_dict, cred_dict):
+        """Check http: rules by calling to a remote server.
+
+        This example implementation simply verifies that the response is
+        exactly 'True'. A custom brain using response codes could easily
+        be implemented.
+
+        """
+        url = match % target_dict
+        data = {'target': json.dumps(target_dict),
+                'credentials': json.dumps(cred_dict)}
+        post_data = urllib.urlencode(data)
+        f = urllib2.urlopen(url, post_data)
+        return f.read() == "True"
diff --git a/tests/unit/test_policy.py b/tests/unit/test_policy.py
new file mode 100644
index 0000000..da70820
--- /dev/null
+++ b/tests/unit/test_policy.py
@@ -0,0 +1,401 @@
+# 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.
+
+"""Test of Policy Engine For Nova"""
+
+import json
+import os.path
+import StringIO
+import unittest
+import urllib
+
+import mock
+import urllib2
+
+from openstack.common import policy
+
+
+class PolicySetAndResetTestCase(unittest.TestCase):
+    def tearDown(self):
+        # Make sure the policy brain is reset for remaining tests
+        policy._BRAIN = None
+
+    def test_set_brain(self):
+        # Make sure the brain is set properly
+        policy._BRAIN = None
+        policy.set_brain('spam')
+        self.assertEqual(policy._BRAIN, 'spam')
+
+    def test_reset(self):
+        # Make sure the brain is set to something
+        policy._BRAIN = 'spam'
+        policy.reset()
+        self.assertEqual(policy._BRAIN, None)
+
+
+class FakeBrain(object):
+    check_result = True
+
+    def check(self, match_list, target_dict, credentials_dict):
+        self.match_list = match_list
+        self.target_dict = target_dict
+        self.credentials_dict = credentials_dict
+        return self.check_result
+
+
+class PolicyEnforceTestCase(unittest.TestCase):
+    def setUp(self):
+        self.fake_brain = FakeBrain()
+        policy._BRAIN = self.fake_brain
+
+    def tearDown(self):
+        policy.reset()
+
+    def check_args(self, match_list, target_dict, credentials_dict):
+        self.assertEqual(self.fake_brain.match_list, match_list)
+        self.assertEqual(self.fake_brain.target_dict, target_dict)
+        self.assertEqual(self.fake_brain.credentials_dict, credentials_dict)
+
+    def test_make_new_brain(self):
+        with mock.patch.object(policy, "Brain") as fake_brain:
+            fake_brain.check.return_value = True
+
+            result = policy.enforce("match", "target", "credentials")
+
+            self.assertNotEqual(policy._BRAIN, None)
+            self.assertEqual(result, True)
+
+    def test_use_existing_brain(self):
+        result = policy.enforce("match", "target", "credentials")
+
+        self.assertNotEqual(policy._BRAIN, None)
+        self.assertEqual(result, True)
+        self.check_args("match", "target", "credentials")
+
+    def test_fail_no_exc(self):
+        self.fake_brain.check_result = False
+        result = policy.enforce("match", "target", "credentials")
+
+        self.assertEqual(result, False)
+        self.check_args("match", "target", "credentials")
+
+    def test_fail_with_exc(self):
+        class TestException(Exception):
+            def __init__(self, *args, **kwargs):
+                self.args = args
+                self.kwargs = kwargs
+
+        self.fake_brain.check_result = False
+        try:
+            result = policy.enforce("match", "target", "credentials",
+                                    TestException, "arg1", "arg2",
+                                    kw1="kwarg1", kw2="kwarg2")
+        except TestException as exc:
+            self.assertEqual(exc.args, ("arg1", "arg2"))
+            self.assertEqual(exc.kwargs, dict(kw1="kwarg1", kw2="kwarg2"))
+        else:
+            self.fail("policy.enforce() failed to raise requested exception")
+
+
+class BrainTestCase(unittest.TestCase):
+    def test_basic_init(self):
+        brain = policy.Brain()
+
+        self.assertEqual(brain.rules, {})
+        self.assertEqual(brain.default_rule, None)
+
+    def test_init_with_args(self):
+        brain = policy.Brain(rules=dict(a="foo", b="bar"), default_rule="a")
+
+        self.assertEqual(brain.rules, dict(a="foo", b="bar"))
+        self.assertEqual(brain.default_rule, "a")
+
+    def test_load_json(self):
+        exemplar = """{
+    "admin_or_owner": [["role:admin"], ["project_id:%(project_id)s"]],
+    "default": []
+}"""
+        brain = policy.Brain.load_json(exemplar, "default")
+
+        self.assertEqual(brain.rules, dict(
+                admin_or_owner=[["role:admin"], ["project_id:%(project_id)s"]],
+                default=[],
+                ))
+        self.assertEqual(brain.default_rule, "default")
+
+    def test_add_rule(self):
+        brain = policy.Brain()
+        brain.add_rule("rule1",
+                       [["role:admin"], ["project_id:%(project_id)s"]])
+
+        self.assertEqual(brain.rules, dict(
+                rule1=[["role:admin"], ["project_id:%(project_id)s"]]))
+
+    def test_check_with_badmatch(self):
+        brain = policy.Brain()
+        result = brain._check("badmatch", "target", "credentials")
+
+        self.assertEqual(result, False)
+
+    def test_check_with_specific(self):
+        self.spam_called = False
+
+        class TestBrain(policy.Brain):
+            def _check_spam(inst, match, target_dict, cred_dict):
+                self.assertEqual(match, "check")
+                self.assertEqual(target_dict, "target")
+                self.assertEqual(cred_dict, "credentials")
+                self.spam_called = True
+
+        brain = TestBrain()
+        result = brain._check("spam:check", "target", "credentials")
+
+        self.assertEqual(self.spam_called, True)
+
+    def test_check_with_generic(self):
+        self.generic_called = False
+
+        class TestBrain(policy.Brain):
+            def _check_generic(inst, match, target_dict, cred_dict):
+                self.assertEqual(match, "spam:check")
+                self.assertEqual(target_dict, "target")
+                self.assertEqual(cred_dict, "credentials")
+                self.generic_called = True
+
+        brain = TestBrain()
+        result = brain._check("spam:check", "target", "credentials")
+
+        self.assertEqual(self.generic_called, True)
+
+    def test_check_empty(self):
+        class TestBrain(policy.Brain):
+            def _check(inst, match, target_dict, cred_dict):
+                self.fail("_check() called for empty match list!")
+
+        brain = TestBrain()
+        result = brain.check([], "target", "credentials")
+
+        self.assertEqual(result, True)
+
+    def stub__check(self):
+        self._check_called = 0
+        self.matches = []
+        self.targets = []
+        self.creds = []
+
+        class TestBrain(policy.Brain):
+            def _check(inst, match, target_dict, cred_dict):
+                self._check_called += 1
+                self.matches.append(match)
+                self.targets.append(target_dict)
+                self.creds.append(cred_dict)
+                return match == "True"
+
+        return TestBrain()
+
+    def test_check_basic_true(self):
+        brain = self.stub__check()
+        result = brain.check(["True"], "target", "creds")
+
+        self.assertEqual(result, True)
+        self.assertEqual(self._check_called, 1)
+        self.assertEqual(self.matches, ["True"])
+        self.assertEqual(self.targets, ["target"])
+        self.assertEqual(self.creds, ["creds"])
+
+    def test_check_basic_false(self):
+        brain = self.stub__check()
+        result = brain.check(["False"], "target", "creds")
+
+        self.assertEqual(result, False)
+        self.assertEqual(self._check_called, 1)
+        self.assertEqual(self.matches, ["False"])
+        self.assertEqual(self.targets, ["target"])
+        self.assertEqual(self.creds, ["creds"])
+
+    def test_check_or_true(self):
+        brain = self.stub__check()
+        result = brain.check([["False"], ["True"], ["False"]],
+                             "target", "creds")
+
+        self.assertEqual(result, True)
+        self.assertEqual(self._check_called, 2)
+        self.assertEqual(self.matches, ["False", "True"])
+        self.assertEqual(self.targets, ["target", "target"])
+        self.assertEqual(self.creds, ["creds", "creds"])
+
+    def test_check_or_false(self):
+        brain = self.stub__check()
+        result = brain.check([["False"], ["False"], ["False"]],
+                             "target", "creds")
+
+        self.assertEqual(result, False)
+        self.assertEqual(self._check_called, 3)
+        self.assertEqual(self.matches, ["False", "False", "False"])
+        self.assertEqual(self.targets, ["target", "target", "target"])
+        self.assertEqual(self.creds, ["creds", "creds", "creds"])
+
+    def test_check_and_true(self):
+        brain = self.stub__check()
+        result = brain.check([["True", "True", "True"]],
+                             "target", "creds")
+
+        self.assertEqual(result, True)
+        self.assertEqual(self._check_called, 3)
+        self.assertEqual(self.matches, ["True", "True", "True"])
+        self.assertEqual(self.targets, ["target", "target", "target"])
+        self.assertEqual(self.creds, ["creds", "creds", "creds"])
+
+    def test_check_and_false(self):
+        brain = self.stub__check()
+        result = brain.check([["True", "True", "False"]],
+                             "target", "creds")
+
+        self.assertEqual(result, False)
+        self.assertEqual(self._check_called, 3)
+        self.assertEqual(self.matches, ["True", "True", "False"])
+        self.assertEqual(self.targets, ["target", "target", "target"])
+        self.assertEqual(self.creds, ["creds", "creds", "creds"])
+
+    def stub__check_rule(self, rules=None, default_rule=None):
+        self.check_called = False
+
+        class TestBrain(policy.Brain):
+            def check(inst, matchs, target_dict, cred_dict):
+                self.check_called = True
+                self.target = target_dict
+                self.cred = cred_dict
+                return matchs
+
+        return TestBrain(rules=rules, default_rule=default_rule)
+
+    def test_rule_no_rules_no_default(self):
+        brain = self.stub__check_rule()
+        result = brain._check_rule("spam", "target", "creds")
+
+        self.assertEqual(result, False)
+        self.assertEqual(self.check_called, False)
+
+    def test_rule_no_rules_default(self):
+        brain = self.stub__check_rule(default_rule="spam")
+        result = brain._check_rule("spam", "target", "creds")
+
+        self.assertEqual(result, False)
+        self.assertEqual(self.check_called, False)
+
+    def test_rule_no_rules_non_default(self):
+        brain = self.stub__check_rule(default_rule="spam")
+        result = brain._check_rule("python", "target", "creds")
+
+        self.assertEqual(self.check_called, True)
+        self.assertEqual(result, ("rule:spam",))
+        self.assertEqual(self.target, "target")
+        self.assertEqual(self.cred, "creds")
+
+    def test_rule_with_rules(self):
+        brain = self.stub__check_rule(rules=dict(spam=["hiho:ni"]))
+        result = brain._check_rule("spam", "target", "creds")
+
+        self.assertEqual(self.check_called, True)
+        self.assertEqual(result, ["hiho:ni"])
+        self.assertEqual(self.target, "target")
+        self.assertEqual(self.cred, "creds")
+
+    def test_role_no_match(self):
+        brain = policy.Brain()
+        result = brain._check_role("SpAm", {}, dict(roles=["a", "b", "c"]))
+
+        self.assertEqual(result, False)
+
+    def test_role_with_match(self):
+        brain = policy.Brain()
+        result = brain._check_role("SpAm", {}, dict(roles=["a", "b", "sPaM"]))
+
+        self.assertEqual(result, True)
+
+    def test_generic_no_key(self):
+        brain = policy.Brain()
+        result = brain._check_generic("tenant:%(tenant_id)s",
+                                      dict(tenant_id="spam"),
+                                      {})
+
+        self.assertEqual(result, False)
+
+    def test_generic_with_key_mismatch(self):
+        brain = policy.Brain()
+        result = brain._check_generic("tenant:%(tenant_id)s",
+                                      dict(tenant_id="spam"),
+                                      dict(tenant="nospam"))
+
+        self.assertEqual(result, False)
+
+    def test_generic_with_key_match(self):
+        brain = policy.Brain()
+        result = brain._check_generic("tenant:%(tenant_id)s",
+                                      dict(tenant_id="spam"),
+                                      dict(tenant="spam"))
+
+        self.assertEqual(result, True)
+
+
+class HttpBrainTestCase(unittest.TestCase):
+    def setUp(self):
+        self.urlopen_result = ""
+
+        def fake_urlopen(url, post_data):
+            self.url = url
+            self.post_data = post_data
+            return StringIO.StringIO(self.urlopen_result)
+
+        self.patcher = mock.patch.object(urllib2, "urlopen", fake_urlopen)
+        self.patcher.start()
+
+    def tearDown(self):
+        self.patcher.stop()
+
+    def decode_post_data(self):
+        result = {}
+        for item in self.post_data.split('&'):
+            key, _sep, value = item.partition('=')
+            result[key] = json.loads(urllib.unquote_plus(value))
+
+        return result
+
+    def test_http_false(self):
+        brain = policy.HttpBrain()
+        result = brain._check_http("//spam.example.org/%(tenant)s",
+                                   dict(tenant="spam"),
+                                   dict(roles=["a", "b", "c"]))
+
+        self.assertEqual(result, False)
+        self.assertEqual(self.url, "//spam.example.org/spam")
+        self.assertEqual(self.decode_post_data(), dict(
+                target=dict(tenant="spam"),
+                credentials=dict(roles=["a", "b", "c"])))
+
+    def test_http_true(self):
+        self.urlopen_result = "True"
+        brain = policy.HttpBrain()
+        result = brain._check_http("//spam.example.org/%(tenant)s",
+                                   dict(tenant="spam"),
+                                   dict(roles=["a", "b", "c"]))
+
+        self.assertEqual(result, True)
+        self.assertEqual(self.url, "//spam.example.org/spam")
+        self.assertEqual(self.decode_post_data(), dict(
+                target=dict(tenant="spam"),
+                credentials=dict(roles=["a", "b", "c"])))