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nova-specs
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Add addendum to Castellan integration specification 

The original Nova specification for integrating Castellan
for key management has merged, but it was suggested that
alternate implementations to the original one may be preferred.

This addendum opens up other options for discussion.

Original specification change id:
I025995584e74c0b2df00841697714c10d1afb674

Change-Id: Ie9c686d9f1ee2e99d3c0b45f3b9b83e1f7ccb00b
This commit is contained in:
Kaitlin Farr 2016-06-30 12:33:51 -04:00
parent 504c10b2b6
commit ebf04e087d
1 changed files with 116 additions and 8 deletions
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124
specs/newton/implemented/use-castellan-key-manager.rst
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@ -54,9 +54,103 @@ agrees that it provides a valuable test fixture.
Alternatives
------------
The alternative is to leave the key manager interface as it is, but this means
that Nova's key manager will not benefit from the updates, new features, and
future additional back ends available in Castellan.
Castellan was integrated into Nova, but ConfKeyManager still remains in the
Nova source code. There are a few options for improving the integration.
The goals in determining a path forward are the following:
* Keep Castellan a key manager interface for production-ready back ends
* Deprecate class-based loading
* Find a back end to serve as a test fixture for encryption features
However, class-based loading is a Castellan feature, and so the spec for
deprecating class-based loading should live in the Castellan/Barbican specs.
The followng are possible alternatives, which solve one or more of the goals:
* Remove and replace ConfKeyManager
One strategy for a path forward is to deprecate and remove ConfKeyManager
and find an alternative back end suitable for testing. The ConfKeyManager
back end reads a single, fixed key from a configuration file. It does not
live in Castellan because ConfKeyManager is very insecure and is only
suitable for testing. It is only useful for basic testing of encryption
features using one key, such as Cinder volume encryption. If any
administrators decided to use ConfKeyManager in their production
deployment, they will be able to store the fixed key in the new back end as
part of the migration necessary after deprecation. Other security features
such as Glance image signing and verification use certificates and cannot
be tested with ConfKeyManager. A back end closer to what is used in
production would provide better testing. The following are options for
replacing ConfKeyManager:
* Option 1: KMIP Castellan back end
The Key Manager Interoperability Protocol (KMIP) is a standardized
protocol for interacting with a key manager. The PyKMIP library [6]
includes not only client code necessary for interacting with a KMIP
hardware device but also a KMIP software server with Keystone
authentication that is useful for functional testing where a hardware
device is not an option. Work on a KMIP Castellan back end has already
started [7], but would need to be completed for this option. The PyKMIP
software server is already used in the Barbican functional gate. New
DevStack gate checks could be configured to use the PyKMIP server for the
encryption Tempest tests, or the existing ones could be modified. This
option satisfies all three of the goals listed above.
* Option 2: Barbican Castellan back end
A Barbican back end already exists for Castellan. This option entails
editing DevStack gate jobs and/or DevStack itself to configure and launch
Barbican. This option is beneficial because it would test encryption
features as they should be used in production, as Barbican is the
recommended back end. However, just 2% of production deployments use
Barbican [4] so it may not make sense to include it in all of the gates.
This option would satisfy all three of the goals listed above.
* Option 3: New database back end
This option is to create a new Castellan test fixture back end that can
store multiple objects in a database. While this option will not provide
a deployment-ready back end, it will be better than ConfKeyManager and
will be able to support functional testing of features such as signed
image verification that need to retrieve certificates. This is an
improvement from using ConfKeyManager because this will allow the key
manager testing code to be closer to what a deployment configuration
would look like. However, this back end does not exist yet, and would
require work to implement the database interactions. Option 1 or Option 2
would require less Castellan development work. Once completed, this
option would satisfy two of the three goals.
* Move ConfKeyManager elsewhere
The community has expressed concern about ConfKeyManager living in the
Nova code base, but moving ConfKeyManager into Castellan is not preferred.
The following are options for if ConfKeyManager cannot be deprecated:
* Option 4: Move ConfKeyManager to Tempest
The Tempest tests are the only place where ConfKeyManager should be used,
so the back end could be moved to Tempest. As long as Castellan provides
an option to register back ends if class-based loading is deprecated,
this option could satisfy all three of the goals above.
* Option 5: Move ConfKeyManager to Castellan
This is not a recommended option. The ConfKeyManager does not support
testing of features such as signed image verification [8], which uses
certificates, not keys. Moving ConfKeyManager to Castellan will push
the problem of not having an adequate testing back end down the road.
* Revert the Castellan integration patch
* Option 6: Revert to nova/keymgr
This is not a recommended option. The key manager interface will be left
as it is in nova/keymgr, but this means that Nova's key manager will not
benefit from the updates, new features, and future additional back ends
available in Castellan. The key manager interface will not be unified
across Nova, as the volume encryption feature and encrypted ephemeral
storage feature will use nova/keymgr, but the image signature
verification feature already uses Castellan.
Data model impact
-----------------
@ -156,22 +250,34 @@ Documentation Impact
====================
These changes will be documented. Nova documentation for disk encryption will
be updated to reference Castellan [4].
be updated to reference Castellan [5].
References
==========
[1] Castellan source code:
[1] Castellan source code
https://github.com/openstack/castellan
[2] Castellan in OpenStack's global requirements:
[2] Castellan in OpenStack's global requirements
https://github.com/openstack/requirements/blob/master/global-requirements.txt
[3] Current Nova key manager implementation
https://github.com/openstack/nova/tree/master/nova/keymgr
[4] Disk encryption configuration reference
http://docs.openstack.org/liberty/config-reference/content/section_volume-encryption.html
[4] April 2016 OpenStack User Survey
http://www.openstack.org/assets/survey/April-2016-User-Survey-Report.pdf
[5] Disk encryption configuration reference
http://docs.openstack.org/liberty/config-reference/content/section_volume-encryption.html
[6] PyKMIP source code
https://github.com/openkmip/pykmip
[7] KMIP backend for Castellan
https://review.openstack.org/#/c/298991/
[8] Glance image signing and verification specification
https://specs.openstack.org/openstack/glance-specs/specs/liberty/image-signing-and-verification-support.html
History
=======
@ -183,3 +289,5 @@ History
- Description
* - Mitaka
- Introduced
* - Newton
- Amended