[S-RBAC] Fix policies for CUD subnets APIs

In new, secure RBAC policies for create subnet there was
rule "ADMIN_OR_PROJECT_MEMBER" used and that was wrong as this rule is
basically allows any member (PROJECT_MEMBER) create subnet in networks
visible to them, not necessarily this project needs to be owner of that
network. So it allowed users to create new subnets in the shared or
provider networks as well.
Now policy for create subnet is ADMIN OR NET_OWNER_MEMBER to avoid that.

Additionally this patch also fixes policies for update and delete subnet
APIs where there was rule NET_OWNER used and that effectively allowed to
update or delete subnet to the network owner who has READER role only.
Now this is also fixed by using NET_OWNER_MEMBER rule instead.

Conflicts:
    neutron/conf/policies/subnet.py

Closes-Bug: #2023679

Change-Id: Ia494872b58f368581fb29fa40b7da17e1071db22
(cherry picked from commit 6e35251)

neutron/conf/policies/subnet.py

@@ -35,13 +35,18 @@
     {'method': 'GET', 'path': RESOURCE_PATH},
 ]
 
+# TODO(slaweq): remove it once network will be added to the
+# EXT_PARENT_RESOURCE_MAPPING in neutron_lib and rule base.PARENT_OWNER_MEMBER
+# will be possible to use instead of RULE_NET_OWNER_MEMBER
+RULE_NET_OWNER_MEMBER = 'role:member and ' + base.RULE_NET_OWNER
+
 
 rules = [
     policy.DocumentedRuleDefault(
         name='create_subnet',
         check_str=base.policy_or(
-            base.ADMIN_OR_PROJECT_MEMBER,
-            base.RULE_NET_OWNER),
+            base.ADMIN,
+            RULE_NET_OWNER_MEMBER),
         scope_types=['project'],
         description='Create a subnet',
         operations=ACTION_POST,
@@ -111,7 +116,7 @@
         name='update_subnet',
         check_str=base.policy_or(
             base.ADMIN_OR_PROJECT_MEMBER,
-            base.RULE_NET_OWNER),
+            RULE_NET_OWNER_MEMBER),
         scope_types=['project'],
         description='Update a subnet',
         operations=ACTION_PUT,
@@ -149,7 +154,7 @@
         name='delete_subnet',
         check_str=base.policy_or(
             base.ADMIN_OR_PROJECT_MEMBER,
-            base.RULE_NET_OWNER),
+            RULE_NET_OWNER_MEMBER),
         scope_types=['project'],
         description='Delete a subnet',
         operations=ACTION_DELETE,

neutron/tests/unit/conf/policies/test_subnet.py

@@ -29,19 +29,33 @@ def setUp(self):
 
         self.network = {
             'id': uuidutils.generate_uuid(),
+            'tenant_id': self.project_id,
             'project_id': self.project_id}
+        self.alt_network = {
+            'id': uuidutils.generate_uuid(),
+            'tenant_id': self.alt_project_id,
+            'project_id': self.alt_project_id}
+
+        networks = {
+            self.network['id']: self.network,
+            self.alt_network['id']: self.alt_network}
 
         self.target = {
             'project_id': self.project_id,
+            'tenant_id': self.project_id,
             'network_id': self.network['id'],
             'ext_parent_network_id': self.network['id']}
         self.alt_target = {
             'project_id': self.alt_project_id,
-            'network_id': self.network['id'],
-            'ext_parent_network_id': self.network['id']}
+            'tenant_id': self.alt_project_id,
+            'network_id': self.alt_network['id'],
+            'ext_parent_network_id': self.alt_network['id']}
+
+        def get_network(context, id, fields=None):
+            return networks.get(id)
 
         self.plugin_mock = mock.Mock()
-        self.plugin_mock.get_network.return_value = self.network
+        self.plugin_mock.get_network.side_effect = get_network
         mock.patch(
             'neutron_lib.plugins.directory.get_plugin',
             return_value=self.plugin_mock).start()