Stop device_owner from being set to 'network:*'

This patch adjusts the FieldCheck class in the policy engine to
allow a regex rule. It then leverages that to prevent users from
setting the device_owner field to anything that starts with
'network:' on networks which they do not own.

This policy adjustment is necessary because any ports with a
device_owner that starts with 'network:' will not have any security
group rules applied because it is assumed they are trusted network
devices (e.g. router ports, DHCP ports, etc). These security rules
include the anti-spoofing protection for DHCP, IPv6 ICMP messages,
and IP headers.

Without this policy adjustment, tenants can abuse this trust when
connected to a shared network with other tenants by setting their
VM port's device_owner field to 'network:<anything>' and hijack other
tenants' traffic via DHCP spoofing or MAC/IP spoofing.

Conflicts:
	etc/policy.json
	neutron/api/v2/attributes.py
	neutron/tests/etc/policy.json
	neutron/tests/unit/test_policy.py

Closes-Bug: #1489111
Change-Id: Ia64cf16142e0e4be44b5b0ed72c8e00792d770f9
(cherry picked from commit 959a2f28cbbfc309381ea9ffb55090da6fb9c78f)

etc/policy.json

@@ -37,7 +37,9 @@
     "update_network:router:external": "rule:admin_only",
     "delete_network": "rule:admin_or_owner",
 
+    "network_device": "field:port:device_owner=~^network:",
     "create_port": "",
+    "create_port:device_owner": "not rule:network_device or rule:admin_or_network_owner",
     "create_port:mac_address": "rule:admin_or_network_owner",
     "create_port:fixed_ips": "rule:admin_or_network_owner",
     "create_port:port_security_enabled": "rule:admin_or_network_owner",
@@ -51,6 +53,7 @@
     "get_port:binding:host_id": "rule:admin_only",
     "get_port:binding:profile": "rule:admin_only",
     "update_port": "rule:admin_or_owner",
+    "update_port:device_owner": "not rule:network_device or rule:admin_or_network_owner",
     "update_port:fixed_ips": "rule:admin_or_network_owner",
     "update_port:port_security_enabled": "rule:admin_or_network_owner",
     "update_port:binding:host_id": "rule:admin_only",

neutron/api/v2/attributes.py

@@ -751,7 +751,7 @@ RESOURCE_ATTRIBUTE_MAP = {
                       'is_visible': True},
         'device_owner': {'allow_post': True, 'allow_put': True,
                          'validate': {'type:string': None},
-                         'default': '',
+                         'default': '', 'enforce_policy': True,
                          'is_visible': True},
         'tenant_id': {'allow_post': True, 'allow_put': False,
                       'validate': {'type:string': None},

neutron/policy.py

@@ -335,6 +335,7 @@ class FieldCheck(policy.Check):
 
         self.field = field
         self.value = conv_func(value)
+        self.regex = re.compile(value[1:]) if value.startswith('~') else None
 
     def __call__(self, target_dict, cred_dict):
         target_value = target_dict.get(self.field)
@@ -345,6 +346,8 @@ class FieldCheck(policy.Check):
                       {'field': self.field,
                        'target_dict': target_dict})
             return False
+        if self.regex:
+            return bool(self.regex.match(target_value))
         return target_value == self.value
 
 

neutron/tests/unit/test_policy.py

@@ -241,6 +241,7 @@ class NeutronPolicyTestCase(base.BaseTestCase):
             "regular_user": "role:user",
             "shared": "field:networks:shared=True",
             "external": "field:networks:router:external=True",
+            "network_device": "field:port:device_owner=~^network:",
             "default": '@',
 
             "create_network": "rule:admin_or_owner",
@@ -251,7 +252,9 @@ class NeutronPolicyTestCase(base.BaseTestCase):
             "get_network": "rule:admin_or_owner or "
                            "rule:shared or "
                            "rule:external",
+            "create_port": "",
             "create_port:mac": "rule:admin_or_network_owner",
+            "create_port:device_owner": "not rule:network_device",
             "create_something": "rule:admin_or_owner",
             "create_something:attr": "rule:admin_or_owner",
             "create_something:attr:sub_attr_1": "rule:admin_or_owner",
@@ -313,6 +316,23 @@ class NeutronPolicyTestCase(base.BaseTestCase):
         self._test_nonadmin_action_on_attr('create', 'shared', True,
                                            exceptions.PolicyNotAuthorized)
 
+    def test_create_port_device_owner_regex(self):
+        uctx = context.Context('', "user", roles=['user'])
+        action = 'create_port'
+        target = {'tenant_id': 'user'}
+        blocked_values = ('network:', 'network:abdef', 'network:dhcp',
+                          'network:router_interface')
+        for val in blocked_values:
+            target['device_owner'] = val
+            self.assertRaises(
+                exceptions.PolicyNotAuthorized, policy.enforce,
+                uctx, action, target
+            )
+        ok_values = ('network', 'networks', 'my_network:test', 'my_network:')
+        for val in ok_values:
+            target['device_owner'] = val
+            self.assertTrue(policy.enforce(uctx, action, target))
+
     def test_nonadmin_read_on_shared_succeeds(self):
         self._test_nonadmin_action_on_attr('get', 'shared', True)