Public bug reported:
During policy testing using Patrole with the new multi-policy support, it
became apparent
that the Neutron policy enforcement code is using the new value of an attribute
(on a PUT
request) to validate access to that same attribute. Here are two scenarios that
expose this problem, using devstack:
Scenario 1:
1. Set up Patrole as a Tempest plugin and set the [patrole] parameters
in
tempest.conf.
2. Set the rbac_test_role to "Member".
3. Change /etc/neutron/policy.json so that "update_network" and
"update_network:shared" are defined as "rule:admin_only" (the
"Member"
role is not allowed to update the network)
4. Change /etc/neutron/policy.json so that "get_network" is defined as
"rule:shared", so that a "Member" is allowed to view only a shared
network, but not a non-shared network.
5. Run the patrole_tempest_plugin.tests.api.network.test_networks_rbac.
NetworksRbacTest.test_update_network_shared test case. This test has
recently been modified to test the multi-policy nature of Neutron's
policy enforcement algorithm.
- The test case expects a 404 NotFound exception to be raised if
the
role being tested ("Member" in this case) is not allowed to
perform
"get_network". A 403 Forbidden exception is expected if the role
is
not allowed to perform either of the "update_network" or
"update_network:shared" actions.
Result:
With the current Neutron code in master, this test fails with the
given
policy because a 403 Forbidden is thrown instead of the expected 404
NotFound exception.
The reason it does not throw the expected 404 is because the
"Member"
role IS allowed to perform "get_network". That is because the
Neutron
policy enforcement code uses the NEW value of the network's "shared"
attribute in order to check if the rule "get_network" is allowed
instead of the original value. The original value is shared=False
as
set by the test case, and the test case is modifying it to True. So
"get_network" should not have been allowed for the Member role here.
See code snippet: https://github.com/openstack/neutron/blob/
9cb68ce7777f3016f6affe0abbc7ebe3b859f7c3/neutron/pecan_wsgi/hooks/
policy_enforcement.py#L123
Scenario 2:
(setup is similar to scenario 1)
The same problem occurs by running the following test case against the
"Member" role:
patrole_tempest_plugin.tests.api.network.test_networks_rbac.
NetworksRbacTest.test_update_network_router_external
using this set of policy rules:
- "update_network" and "update_network:router:external" defined as
"rule:admin_only"
- "get_network" is defined as "rule:external", so that a "Member" is
allowed to view only external networks.
Result:
Although 404 is expected to be thrown by Neutron due to the
"get_network" rule, Neutron actually throws a 403 exception, so the
test case fails. That is because the Neutron policy enforcement code
uses the NEW value of the network's "external" attribute in order to
check if the rule "get_network" is allowed instead of the original
value. The original value is external=False as set by the test case,
and the test case is modifying it to True. So "get_network" should
not have been allowed for the Member role here.
** Affects: neutron
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1779003
Title:
Policy check using new attribute value to validate access to the same
attribute
Status in neutron:
New
Bug description:
During policy testing using Patrole with the new multi-policy support, it
became apparent
that the Neutron policy enforcement code is using the new value of an
attribute (on a PUT
request) to validate access to that same attribute. Here are two scenarios
that expose this problem, using devstack:
Scenario 1:
1. Set up Patrole as a Tempest plugin and set the [patrole] parameters
in
tempest.conf.
2. Set the rbac_test_role to "Member".
3. Change /etc/neutron/policy.json so that "update_network" and
"update_network:shared" are defined as "rule:admin_only" (the
"Member"
role is not allowed to update the network)
4. Change /etc/neutron/policy.json so that "get_network" is defined as
"rule:shared", so that a "Member" is allowed to view only a shared
network, but not a non-shared network.
5. Run the patrole_tempest_plugin.tests.api.network.test_networks_rbac.
NetworksRbacTest.test_update_network_shared test case. This test
has
recently been modified to test the multi-policy nature of Neutron's
policy enforcement algorithm.
- The test case expects a 404 NotFound exception to be raised if
the
role being tested ("Member" in this case) is not allowed to
perform
"get_network". A 403 Forbidden exception is expected if the
role is
not allowed to perform either of the "update_network" or
"update_network:shared" actions.
Result:
With the current Neutron code in master, this test fails with the
given
policy because a 403 Forbidden is thrown instead of the expected
404
NotFound exception.
The reason it does not throw the expected 404 is because the
"Member"
role IS allowed to perform "get_network". That is because the
Neutron
policy enforcement code uses the NEW value of the network's
"shared"
attribute in order to check if the rule "get_network" is allowed
instead of the original value. The original value is shared=False
as
set by the test case, and the test case is modifying it to True.
So
"get_network" should not have been allowed for the Member role
here.
See code snippet: https://github.com/openstack/neutron/blob/
9cb68ce7777f3016f6affe0abbc7ebe3b859f7c3/neutron/pecan_wsgi/hooks/
policy_enforcement.py#L123
Scenario 2:
(setup is similar to scenario 1)
The same problem occurs by running the following test case against the
"Member" role:
patrole_tempest_plugin.tests.api.network.test_networks_rbac.
NetworksRbacTest.test_update_network_router_external
using this set of policy rules:
- "update_network" and "update_network:router:external" defined as
"rule:admin_only"
- "get_network" is defined as "rule:external", so that a "Member" is
allowed to view only external networks.
Result:
Although 404 is expected to be thrown by Neutron due to the
"get_network" rule, Neutron actually throws a 403 exception, so
the
test case fails. That is because the Neutron policy enforcement
code
uses the NEW value of the network's "external" attribute in order
to
check if the rule "get_network" is allowed instead of the original
value. The original value is external=False as set by the test
case,
and the test case is modifying it to True. So "get_network" should
not have been allowed for the Member role here.
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